[One .NET] Do not preserve IO stream adapter/invoker (#5449)

Context: #5167
Context: #5206

The following types are accessed through the `CallbackCode` type
in `src/Mono.Android.Export` via System.Reflection:

  * `Android.Runtime.InputStreamAdapter`
  * `Android.Runtime.InputStreamInvoker`
  * `Android.Runtime.OutputStreamAdapter`
  * `Android.Runtime.OutputStreamInvoker`

Historically the use of these types via Reflection required that they
always be preserved, just in case `Mono.Android.Export.dll` was used.

.NET 6 ILLink is able to detect such reflection use.  These types no
longer need to be explicitly preserved in all circumstances.

Stop explicitly preserving these types, and rely on ILLink to
preserve them when `Mono.Android.Export.dll` is used.

This change reduces the `.apk` size in a common situation, when
`Mono.Android.Export.dll` is not used.

apk size comparison, BuildReleaseArm64False test:

	> apkdiff -f -e dll$ before.apk after.apk
	Size difference in bytes ([*1] apk1 only, [*2] apk2 only):
	  -          80 assemblies/System.Console.dll
	  -         129 assemblies/Java.Interop.dll
	  -       1,237 assemblies/System.Private.CoreLib.dll
	  -       6,093 assemblies/Mono.Android.dll
	Summary:
	  -       7,539 Assemblies -1.01% (of 749,078)

src/Microsoft.Android.Sdk.ILLink/PreserveLists/Mono.Android.xml

@@ -5,8 +5,6 @@
 		<type fullname="Android.Runtime.GeneratedDummyHost" />
 		<type fullname="Android.Runtime.GeneratedEnumAttribute" />
 		<type fullname="Android.Runtime.IJavaObject" />
-		<type fullname="Android.Runtime.InputStreamAdapter" />
-		<type fullname="Android.Runtime.InputStreamInvoker" />
 		<type fullname="Android.Runtime.JNIEnv">
 			<method name="Exit" />
 			<method name="Initialize" />
@@ -34,8 +32,6 @@
 		<type fullname="Android.Runtime.LogLevel" />
 		<type fullname="Android.Runtime.LogCategories" />
 		<type fullname="Android.Runtime.NamespaceMappingAttribute" />
-		<type fullname="Android.Runtime.OutputStreamAdapter" />
-		<type fullname="Android.Runtime.OutputStreamInvoker" />
 		<type fullname="Android.Runtime.PreserveAttribute" />
 		<type fullname="Android.Runtime.RaiseThrowableEventArgs" />
 		<type fullname="Android.Runtime.RegisterAttribute" />