Commander: add annotation and entity type to view model

These are to support displaying hotkeys and tagging different types of
result with specific icons.

Bug: 1014639
Change-Id: I93f432a2368c25285dd714c4f2fbdaef96434a33
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2403661


Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Commit-Queue: Leonard Grey <lgrey@chromium.org>
Cr-Commit-Position: refs/heads/master@{#805887}