Reuse LocalePickerWithRegion in app language selection

- (LocalePickerWithRegion) Only list the language that supported by app
- Add "System language" option
- Add current app locale into suggestion list
- Sort locales by these priorities:
  1. Current app's locale
  2. System language
  3. Suggested language
  4. Supported languages

Bug: 223090003
Test: Manual
- (system languages page)
    Check Settings-> System -> Languages -> Languages
- (pre-apps language page)
    Check Settings-> System -> Languages -> Apps Languages
- Add unit test in follow CL(tracing in b/224747202)
Change-Id: I8dc9f73811dbf653b32773fb98ddb2e4656a4432