Run unit tests on Android

[bruno-garcia]

The net6.0-android target isn't tested

From @mattjohnsonpint's comment in this PR: #1703 (comment)

Hi. I have another big PR with more MAUI stuff coming shortly that includes the deployment flag. But if you can find a way to get device tests going that would be amazing.

Currently, I can only write unit tests that run on net6.0 target, but there's a lot of code we'll want to tests that is only applicable under a specific device target, such as net6.0-android.

I think we want to do something like what the MAUI team is doing here: https://github.com/dotnet/maui/tree/main/src/TestUtils

Looks like others are trying this as well. See dotnet/maui#3552 (comment)

An attempt was done in the past, in this PR:

• test: sentry tests android net6 #967

Ideally we'd use xharness.

[bruno-garcia]

.NET runtime (core lib) uses xharness too:

https://github.com/dotnet/runtime/blob/main/src/libraries/Common/tests/AndroidTestRunner/AndroidTestRunner.cs

https://github.com/dotnet/runtime/blob/098b14239fa8cb1f64c7790b7f1f095151d00df8/src/libraries/Common/tests/AndroidTestRunner/AndroidTestRunner.csproj#L9