[Mono.Android] Emit only summary XML, not full XML

Context: dotnet#5253 (comment)
Context: dotnet/java-interop#687 (comment)
Context: dotnet/java-interop@a65b8ab

It looks like only emitting `<summary/>`, `<param/>`, `<returns/>`,
and `<exception/>` is *much* faster than trying to do full
`<remarks/>`.

Update the `generator.exe` invocation to use
`generator --doc-comment-style=summary`, which will hopefully
speed things up.

src/Mono.Android/Mono.Android.csproj

@@ -25,12 +25,16 @@
   </PropertyGroup>
 
   <PropertyGroup>
+    <!--
     <IncludeAndroidJavadoc Condition=" '$(IncludeAndroidJavadoc)' == '' And '$(CONVERT_JAVADOC_TO_XMLDOC)' == 'true' And '$(AndroidFrameworkVersion)' == '$(AndroidLatestStableFrameworkVersion)'">True</IncludeAndroidJavadoc>
+    -->
+    <!-- TODO: replace with above; for CI timing purposes only! -->
+    <IncludeAndroidJavadoc Condition=" '$(IncludeAndroidJavadoc)' == '' And '$(AndroidFrameworkVersion)' == '$(AndroidLatestStableFrameworkVersion)'">True</IncludeAndroidJavadoc>
   </PropertyGroup>
 
   <PropertyGroup Condition=" '$(IncludeAndroidJavadoc)' == 'True' ">
     <DocumentationFile>$(OutputPath)Mono.Android.xml</DocumentationFile>
-    <NoWarn>CS1573;CS1591</NoWarn>
+    <NoWarn>CS1572;CS1573;CS1574;CS1587;CS1591;</NoWarn>
   </PropertyGroup>
 
   <PropertyGroup Condition=" '$(TargetFramework)' == 'monoandroid10' ">

src/Mono.Android/Mono.Android.targets

@@ -145,7 +145,7 @@
     </ItemGroup>
     <PropertyGroup>
       <Generator>"$(XAInstallPrefix)xbuild\Xamarin\Android\generator.exe"</Generator>
-      <_GenFlags>--public --product-version=7</_GenFlags>
+      <_GenFlags>--doc-comment-style=summary --public --product-version=7</_GenFlags>
       <_ApiLevel>--api-level=$(AndroidApiLevel)</_ApiLevel>
       <_Out>-o "$(IntermediateOutputPath)mcw"</_Out>
       <_Codegen>--codegen-target=XAJavaInterop1</_Codegen>