[Mono.Android] fix crash on startup with EnableLLVM

`dotnet new android` apps would crash on startup when built with
`-c Release -p:EnableLLVM=true`:

    07-20 08:55:44.642  2983  2983 F monodroid-assembly: Internal p/invoke symbol 'java-interop @ java_interop_jvm_list' (hash: 0x58c48fc8b89cb484) not found in compile-time map.
    ...
    07-20 08:55:44.834  3004  3004 F DEBUG   : signal 6 (SIGABRT), code -1 (SI_QUEUE), fault addr --------
    07-20 08:55:44.834  3004  3004 F DEBUG   : Abort message: 'Internal p/invoke symbol 'java-interop @ java_interop_jvm_list' (hash: 0x58c48fc8b89cb484) not found in compile-time map.'

`java_interop_jvm_list` should *never* be called on Android, it is the
result of `new AndroidRuntime()` having not been called yet?

The problem being that the static `Android.App.Application.cctor` was
somehow running *before* `JNIEnv.Initialize()` was complete? And this
only happens with LLVM?

Reviewing the code:

    [UnmanagedCallersOnly]
    internal static unsafe void Initialize (JnienvInitializeArgs* args)
    {
        //...
        SynchronizationContext.SetSynchronizationContext (Android.App.Application.SynchronizationContext);
    }

We do indeed access `Android.App.Application`...

To fix this, we can move this to a new method decorated with
`MethodImplOptions.NoInlining`. Apps built with LLVM now launch for
me.

We can also enable the LLVM `Mono.Android-Tests` again.

build-tools/automation/azure-pipelines.yaml

@@ -691,13 +691,11 @@ stages:
 
     - template: yaml-templates/apk-instrumentation.yaml
       parameters:
-        # TODO: disable LLVM test, see: https://github.com/dotnet/runtime/issues/68914
-        condition: false
         configuration: $(XA.Build.Configuration)
         testName: Mono.Android.NET_Tests-AotLlvm
         project: tests/Mono.Android-Tests/Runtime-Microsoft.Android.Sdk/Mono.Android.NET-Tests.csproj
         testResultsFiles: TestResult-Mono.Android.NET_Tests-$(XA.Build.Configuration)AotLlvm.xml
-        extraBuildArgs: -p:TestsFlavor=AotLlvm -p:EnableLlvm=true
+        extraBuildArgs: -p:TestsFlavor=AotLlvm -p:EnableLlvm=true -p:AndroidEnableProfiledAot=false
         artifactSource: bin/Test$(XA.Build.Configuration)/$(DotNetTargetFramework)-android/Mono.Android.NET_Tests-Signed.aab
         artifactFolder: $(DotNetTargetFramework)-AotLlvm
         useDotNet: true

src/Mono.Android/Android.Runtime/JNIEnv.cs

@@ -196,10 +196,17 @@ internal static unsafe void Initialize (JnienvInitializeArgs* args)
 			}
 
 #if !MONOANDROID1_0
-			SynchronizationContext.SetSynchronizationContext (Android.App.Application.SynchronizationContext);
+			SetSynchronizationContext ();
 #endif
 		}
 
+#if !MONOANDROID1_0
+		// NOTE: prevents Android.App.Application static ctor from running
+		[MethodImpl (MethodImplOptions.NoInlining)]
+		static void SetSynchronizationContext () =>
+			SynchronizationContext.SetSynchronizationContext (Android.App.Application.SynchronizationContext);
+#endif
+
 		internal static void Exit ()
 		{
 			/* Manually dispose surfaced objects and close the current JniEnvironment to