…cations. (dotnet#5708)

Context: https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1288717
Context: xamarin/monodroid@83de4b4

Changes: xamarin/monodroid@b2a750a...4163ee9

  * xamarin/monodroid@4163ee947: [Xamarin.Android.Build.Tasks] Support FastDev for System Apps (dotnet#1177) (dotnet#1186)
  * xamarin/monodroid@947c6ef72: Bump to xamarin/xamarin-android/d16-9@877f5727 (dotnet#1183)

The new fast deployment system (xamarin/monodroid@767f6471) broke
fast deployment for system-installed applications.

This is fixed in xamarin/monodroid@4163ee94.

Adds unit tests to stop this kind of regression in the future.

In order to install a `system` application we need a few things:

 1. The emulator MUST be started with the `-system-writable` argument

 2. The `.apk` needs to be signed with a platform keystore, found at:
    https://github.com/aosp-mirror/platform_build/tree/master/target/product/security

 3. `AndroidManifest.xml` must set
    [`/manifest/@android:sharedUserId`][0] to `android.uid.system`:

        <manifest xmlns:android="http://schemas.android.com/apk/res/android"
            android:sharedUserId="android.uid.system"
            …>
        </manifest>

See also:

  * https://medium.com/xrpractices/android-system-apps-development-d73bedfb8def

[0]: https://developer.android.com/guide/topics/manifest/manifest-element#uid

…5571)

Context: https://devdiv.visualstudio.com/DevDiv/_build/results?buildId=4422361&view=ms.vss-test-web.build-test-results-tab&runId=18547936&resultId=100086&paneView=debug

We had an MSBuild test failing under .NET 6:

    MSBuildDeviceIntegration On Device - macOS - One .NET > SwitchConfigurationsShouldRedeploy
    fastdev directory should NOT exist for Release builds.
    Expected string length 0 but was 4970. Strings differ at index 0.
    Expected: <string.Empty>
    But was:  "Java.Interop.dll\nMicrosoft.CSharp.dll\nMicrosoft.VisualBasic.C..."

This was because a supposed `Release` build was skipping the `_Upload`
target completely:

    Skipping target "_Upload" because all output files are up-to-date with respect to the input files.
    Input files: bin\Debug\UnnamedProject.UnnamedProject-Signed.apk...

It appears that toggling `XamarinProject.IsRelease` is not triggering
the correct files to save when the tests run under .NET 6.

Under "legacy" Xamarin.Android, the tests simply put this at the top
of the `.csproj`:

      <Configuration>Debug</Configuration>
    ...
    <Import Project="$(MSBuildExtensionsPath)\Xamarin\Android\Xamarin.Android.CSharp.targets" />

This won't work in short-form MSBuild projects, because the `.csproj`
is effectively:

    <Import Sdk="Microsoft.NET.Sdk" Project="Sdk.props" />
    ...
      <Configuration>Debug</Configuration>
    ...
    <Import Sdk="Microsoft.NET.Sdk" Project="Sdk.targets" />

For things to work properly, we need `$(Configuration)` to be set
*before* `Microsoft.NET.Sdk/Sdk.props`.

So we put `$(Configuration)` in a `Directory.Build.props` to solve
this ordering problem. Unfortunately, we were not calling `Touch()` on
this file when `XamarinProject.IsRelease` changes.

After making this change, `SwitchConfigurationsShouldRedeploy` passes.