Add aconfig flag support for android_library

This change adds the support that was added to android_app in
https://r.android.com/2854663 for android_library modules.

Implementation details:
- Move `Flags_packages` to aaptProperties, so that it can be utilized
  for both android_app and android_library.
- Wrap `VisitDirectDeps` of aconfig_declarations to a function that
  takes a ModuleContext as an input, so that it can be utilized in the
  `GenerateAndroidBuildActions` of both android_app and android_library.

Test: m nothing --no-skip-soong-tests
Bug: 330222981
Change-Id: I8a755f5ca615c8a1651afcd2ec441fc9fbd82c61