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
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:71628170ad71416d36508d9b815b6f53d214ab4e)
Merged-In: I52788abd4f09bb32259b00f915dbe704ac0442af
Change-Id: I52788abd4f09bb32259b00f915dbe704ac0442af