Enable cached ReadyToRun for CoreCLR Android Debug builds

[Copilot]

CoreCLR Debug builds now precompile stable framework and Android SDK assemblies while preserving user assemblies as IL for debugging and incremental development.

• ReadyToRun defaults

  • Enable non-composite ReadyToRun for CoreCLR Debug applications.
  • Preserve composite ReadyToRun for Release builds and explicit opt-out behavior.

• Assembly selection

  • Compile managed runtime-pack assemblies, including System.Private.CoreLib.dll.
  • Exclude application and NuGet package assemblies from crossgen2.

• Incremental builds

  • Reuse per-RID ReadyToRun outputs through the existing incremental pipeline.
  • Prevent user-code changes from invalidating framework ReadyToRun outputs.

• Fast deployment

  • Package cached framework images through the existing fast deployment path.
  • Suppress the incompatible-configuration warning for this supported CoreCLR Debug scenario.

• Coverage

  • Verify framework assemblies contain ReadyToRun images.
  • Verify user assemblies remain IL.
  • Verify user-only changes skip crossgen2 and retain cached framework images.

[kotlarmilos]

#12117