[ios/android] Improve internal support for iOS/Android testing and verification

[ivanpovazan]

Description

Our internal support for iOS/Android testing and verification requires refactoring.
This is mostly related to iOS/Android:

• sample applications under src/mono/sample/* - used for performance testing and inner-dev loops
• application bundlers
• build integration files - used when building samples, runtime, libraries and functional tests
• functional tests

Tasks

The following list of tasks is tentative.

• Enable HelloAndroid to use AndroidBuild.targets (covered in: [android] Internal Android sample build improvements and CoreCLR support #111545)
• Adapt HelloAndroid, AndroidAppBuilder to support targeting non-Mono runtimes (covered in: Beginnings of native Android build #110471)
• Adapt HelloiOS, AppleAppBuilder to support targeting non-Mono runtimes (covered in: Add support for building CoreCLR for MacCatalyst/iOS simulator #109928)
• [mono][tests] Stop using CoreCLR-specific properties when building mono runtime tests #111919
• [mono] Unify mobile build integration files and sample apps for non-Mono runtimes #111923
• Introduce functional test(s) for all supported platforms/runtimes (library mode should be covered where applicable) that run regularly on CI
• Consider moving out iOS/Android samples from Mono subdir
• Fix Android startup measurements [Android] Decouple runtime initialization and entry point execution for Android sample #111742

[ivanpovazan]

/cc: @filipnavara

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