Implement the method for time short string

- Add new charging string
- Implement the method to convert remaining time milliseconds to short
  string format, e.g. "1:30PM"
- Increase some class variable to protect in
  KeyguardIndicationController

Test: Unit Test and Manual test
Bug: 328546483
Flag: NA

Change-Id: I52788abd4f09bb32259b00f915dbe704ac0442af