Add keyboard shortcuts to move between revisions
- Added tabindex on yellow and blue knobs to enable tabbing
- Used some of the logic of draggable functionality to support moving between revisions with keyboard shortcuts
- Also changed the source order of old and new pointer. Old pointer comes first in the DOM
Bug: T162119
Change-Id: I4d8db2352915c44aa11617edea5bcb0ac92ddc93