Adding a simple ImageSerial tracking map in our RenderPass allows us
to know when we do or do not need to close the RenderPass on a new
Image access. This simple tracking scheme improves Manhattan
performance by up to 25% on Android. The improved perf comes from
reducing our RenderPass count (23->18 RenderPasses in our capture
scene).

Adds a FastUnorderedSet class to manage the used RP Image serials.

Updates the Query helpers to explicitly flush the RP before inserting
queries.

Bug: angleproject:4911
Change-Id: I0c34fc8e307514ebdf3e81e08d8e5aedb70ebe8f
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2334346Reviewed-by: Charlie Lao <cclao@google.com>
Reviewed-by: Tim Van Patten <timvp@google.com>
Commit-Queue: Jamie Madill <jmadill@chromium.org>