StaticKCM: Add KEY_CHARACTER_MAP_NAME.

This CL adds KEY_CHARACTER_MAP_NAME to ArcInputBridgeProtocol.
Currently KeyCharacterMap is dynamically generated at runtime. StaticKCM
will change this to use statically genearted KCM files.

Design doc: go/arc-static-kcm-converter

Test: None
Bug: 122704772
Change-Id: Ibd7cf107b9cbd33a6f6581681a1c60f3cdeb1cca