Bug fixed in
https://chromium-review.googlesource.com/c/angle/angle/+/2961690
triggers only in the following situation:

- Context 1: draw indexed -> clears index dirty bit
- Context 1: change state in such a way that closing the render pass is
             deferred to dirty bit handling (for example, change FBO)
- Context 1: issue a non-indexed draw call.  This closes the render pass
             and starts a new one -> bug was that the index dirty bit
             was not set
- Context 2: flush the command buffer, which submits the previous render
             pass of context 1 (which contained vkCmdBindIndexBuffer).
             The primary command buffer is now reset.
- Context 1: issue an indexed draw call.  Since the index dirty bit was
             not set, this was missing the vkCmdBindIndexBuffer call.

This change implements a regression test based on the above scenario.

Bug: chromium:1183068
Bug: chromium:1190493
Change-Id: I729bd48cd6df2621ca763f6231023a52ac08b0fb
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2963836Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Charlie Lao <cclao@google.com>
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>