[Custom Key Glyph] Return all the maps in keyboard glyph maps xml

This CL fixes below issues
1. loadGlyphMapDataList only returns the first map, it should return all
   maps
2. add new API getDrawableForModifierState for modifier state like KeyEvent.META_META_ON

Bug: 375701353
Test: KeyboardGlyphManagerTests
Flag: com.android.hardware.input.keyboard_glyph_map
Change-Id: I5753ed2769f8039b3cbb9935f73110cdfb4f5e2c