[ci] Fix remaining permanent CI warnings. (#8595)

Fix various CI warnings, such as:

	Specifying an exact version is not recommended on Microsoft-Hosted agents.
	  Patch versions of Python can be replaced by new ones on Hosted agents
	  without notice, which will cause builds to fail unexpectedly.
	  It is recommended to specify only major or major and minor version (Example: `3` or `3.9`)

Fix: only specify `major.minor` as requested.

Or [MSB4011][0]:

	build-tools\scripts\RunTests.targets(3,3): Warning MSB4011:
	  "C:\a\_work\1\s\Directory.Build.props" cannot be imported again.
	  It was already imported at "C:\a\_work\1\s\build-tools\scripts\PrepareWindows.targets(3,3)".
	  This is most likely a build authoring error. This subsequent import will be ignored. 
	build-tools\scripts\RunTests.targets(7,3): Warning MSB4011:
	  "C:\a\_work\1\s\Configuration.props" cannot be imported again.
	  It was already imported at "C:\a\_work\1\s\build-tools\scripts\PrepareWindows.targets(11,3)".
	  This is most likely a build authoring error. This subsequent import will be ignored.
	tests\api-compatibility\api-compatibility.targets(3,3): Warning MSB4011:
	  "C:\a\_work\1\s\Configuration.props" cannot be imported again.
	  It was already imported at "C:\a\_work\1\s\build-tools\scripts\PrepareWindows.targets(11,3)".
	  This is most likely a build authoring error. This subsequent import will be ignored.

Fix: add a flag denoting that we have already imported a project and
a `Condition` to prevent duplicate imports.

Or [CS8604][1]:

	build-tools\xaprepare\xaprepare\Application\Context.cs(608,42): Warning CS8604:
	Possible null reference argument for parameter 'path1' in 'string Path.Combine(string path1, string path2)'.

Fix: add null check.

Or:

	EXEC(0,0): Warning : dotnet archive URL https://dotnetcli.azureedge.net/dotnet/Sdk/9.0.100-alpha.1.23610.1/dotnet-sdk-9.0.100-alpha.1.23610.1-win-x64.zip not found

Fix: checking multiple URLs is part of the expected flow;
downgrade the message to "info".

Or:

	EXEC(0,0): Warning : Duplicate Third Party Notice 'IronyProject/Irony'
	  (old class: Xamarin.Android.Prepare.XamarinAndroidBuildTasks_IronyProject_Irony_TPN;
	   new class: Xamarin.Android.Prepare.XamarinAndroidToolsAidl_IronyProject_Irony_TPN)

Fix: multiple projects may use the same dependencies;
downgrade the message to "info".

The remaining CI warnings are temporary because our MAUI integration
tests are currently failing:

![image](https://github.com/xamarin/xamarin-android/assets/179295/1455637d-3f8d-4582-b5c8-50a23b1b8b25)

[0]: https://learn.microsoft.com/visualstudio/msbuild/errors/msb4011
[1]: https://learn.microsoft.com/dotnet/csharp/language-reference/compiler-messages/nullable-warnings#possible-null-assigned-to-a-nonnullable-reference

Configuration.props

@@ -17,6 +17,7 @@
       Condition="Exists('$(MSBuildThisFileDirectory)Configuration.Override.props')"
   />
   <PropertyGroup>
+    <ConfigurationPropsImported>true</ConfigurationPropsImported>
     <!-- TFV for all projects, try v4.7.2 but fallback if needed -->
     <_StandardLibraryPath Condition=" '$(TargetFrameworkVersion)' == '' ">$([Microsoft.Build.Utilities.ToolLocationHelper]::GetPathToStandardLibraries('.NETFramework', 'v4.7.2', ''))</_StandardLibraryPath>
     <TargetFrameworkVersion Condition=" '$(TargetFrameworkVersion)' == '' And '$(UsingMicrosoftNETSdk)' != 'true' And '$(_StandardLibraryPath)' != '' ">v4.7.2</TargetFrameworkVersion>

Directory.Build.props

@@ -1,6 +1,7 @@
 <Project>
 
   <PropertyGroup>
+    <DirectoryBuildPropsImported>true</DirectoryBuildPropsImported>
     <DotNetTargetFrameworkVersion>9.0</DotNetTargetFrameworkVersion>
     <DotNetTargetFramework>net$(DotNetTargetFrameworkVersion)</DotNetTargetFramework>
     <DotNetAndroidTargetFramework>$(DotNetTargetFramework)-android</DotNetAndroidTargetFramework>

build-tools/automation/yaml-templates/install-microbuild-tooling.yaml

@@ -11,7 +11,7 @@ steps:
 
 - task: UsePythonVersion@0
   inputs:
-    versionSpec: 3.11.x
+    versionSpec: 3.11
 
 # ESRP signing requires minimum azure client version 2.8.0
 - template: azure-tools/az-client-update.yml@yaml-templates

build-tools/scripts/RunTests.targets

@@ -1,10 +1,10 @@
 <?xml version="1.0" encoding="utf-8"?>
 <Project DefaultTargets="RunAllTests" ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
-  <Import Project="$([MSBuild]::GetPathOfFileAbove('Directory.Build.props'))" />
+  <Import Project="$([MSBuild]::GetPathOfFileAbove('Directory.Build.props'))" Condition=" '$(DirectoryBuildPropsImported)' != 'true' " />
   <PropertyGroup>
     <_TopDir>$(MSBuildThisFileDirectory)..\..</_TopDir>
   </PropertyGroup>
-  <Import Project="$(_TopDir)\Configuration.props" />
+  <Import Project="$(_TopDir)\Configuration.props" Condition=" '$(ConfigurationPropsImported)' != 'true' " />
   <UsingTask AssemblyFile="$(PrepTasksAssembly)" TaskName="Xamarin.Android.BuildTools.PrepTasks.RunParallelTargets" />
   <UsingTask AssemblyFile="$(PrepTasksAssembly)" TaskName="Xamarin.Android.BuildTools.PrepTasks.SetEnvironmentVariable" />
   <PropertyGroup>

build-tools/xaprepare/xaprepare/Application/Context.cs

@@ -605,7 +605,8 @@ string GetLogDirectory ()
 
 		void WriteBuildToolsInventoryCsv ()
 		{
-			var inventoryFilePath = Path.Combine (Path.GetDirectoryName (MainLogFilePath), "buildtoolsinventory.csv");
+			var mainLogFileDirectory = Path.GetDirectoryName (MainLogFilePath) ?? throw new ArgumentException ("Could not get directory for MainLogFilePath");
+			var inventoryFilePath = Path.Combine (mainLogFileDirectory, "buildtoolsinventory.csv");
 			var lines = new List<string> {
 				"BuildToolName,BuildToolVersion",
 			};

build-tools/xaprepare/xaprepare/Steps/Step_InstallDotNetPreview.cs

@@ -119,7 +119,7 @@ async Task<bool> DownloadDotNetArchive (Context context, string archiveDestinati
 			(bool success, ulong size, HttpStatusCode status) = await Utilities.GetDownloadSizeWithStatus (archiveUrl);
 			if (!success) {
 				if (status == HttpStatusCode.NotFound) {
-					Log.WarningLine ($"dotnet archive URL {archiveUrl} not found");
+					Log.InfoLine ($"dotnet archive URL {archiveUrl} not found");
 					return false;
 				} else {
 					Log.WarningLine ($"Failed to obtain dotnet archive size. HTTP status code: {status} ({(int)status})");

build-tools/xaprepare/xaprepare/Steps/Step_ThirdPartyNotices.cs

@@ -172,7 +172,7 @@ void ProcessTPN (SortedDictionary <string, ThirdPartyNotice> licenses, ThirdPart
 			Log.StatusLine ($"  {Context.Instance.Characters.Bullet} Processing: ", tpn.Name, ConsoleColor.Gray, ConsoleColor.White);
 
 			if (licenses.ContainsKey (tpn.Name)) {
-				Log.WarningLine ($"Duplicate Third Party Notice '{tpn.Name}' (old class: {licenses [tpn.Name]}; new class: {tpn})");
+				Log.InfoLine ($"Duplicate Third Party Notice '{tpn.Name}' (old class: {licenses [tpn.Name]}; new class: {tpn})");
 				return;
 			}
 

tests/api-compatibility/api-compatibility.targets

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <Project DefaultTargets="Build" ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
-  <Import Project="..\..\Configuration.props" />
+  <Import Project="..\..\Configuration.props" Condition=" '$(ConfigurationPropsImported)' != 'true' " />
   <UsingTask AssemblyFile="$(BootstrapTasksAssembly)" TaskName="Xamarin.Android.Tools.BootstrapTasks.Zip" />
   <Target Name="UpdateMonoAndroidContract">
     <Error