This simplifies the dirty state updates in VertexArrayVk. It also lets
us use a smaller dirty bit mask when a single attribute is marked dirty
in a vertex array.

Improves performance by about 1-2% in the VBO state change test. Will
allow for better performance using a pipeline transition table.

Bug: angleproject:3013
Change-Id: I25c5172b3f41b7abac6b8273c8f9cd42eb46cc9f
Reviewed-on: https://chromium-review.googlesource.com/c/1403958Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>