Add internal APIs to support modifier key remapping

Add support for remapping 4 modifier keys: Ctrl, Meta, Alt and
Shift to one another.
Use new addKeyRemapping native API to add key remappings for
supported modifier keys. Explicitly define supported modifier
keys to prevent misuse to remap other Android key codes.

Test: atest KeyboardLayoutChangeTest
Bug: 252812993
Change-Id: I6d03b7dba37b9ec9cef3dca98f7081ef0a378447