Implemented custom focus states for shortcut helper categories

+ made shortcuts focusable so right hand panel is navigatable with
  keyboard

+ add focus states for categories on left hand panel

+ add focus states for shortcuts on right hand panel

+ updated left hand side panel to 200dp to match UI specs

Bug: 352305030
Test: Manual - Open shortcut helper, using tab+ arrow keys navigate
through shortcut helper, ensure focus outline appears on categories,
shortcuts and keyboard settings.
Flag: com.android.systemui.keyboard_shortcut_helper_rewrite

Change-Id: Idb57f887faa111c6e181fdd9c9d5516a2e88ad8e