Align shortcut helper components to spec

 - update left/right margins
 - Reconcile key icon/text views with small-screen helper
 - Replace non-meta icons with text labels
 - various padding, sizing, colour tweaks to align with design spec
 - Fix a bug where the wrong context was used to load resources
 - Remove overscroll on shortcut list view
 - Replace vertical bar with string for shortcut separator
 - Remove '+' between keys
 - Update arrow key strings

Bug: 286538767
Test: inspection
Flag: NA
Change-Id: I18e65a8c7f16f368c9774f399c458749b1f4ce80