This cleans up the confusing releaseResource/releaseObject pair in the
RendererVk class. It also makes getQueueSerial private in ResourceVk
but keeps a public isResourceInUse API for external use.

Bug: angleproject:2539
Change-Id: I6b4f24db16e36130a85ef03fc2c3b26d8d9e1fba
Reviewed-on: https://chromium-review.googlesource.com/1069291
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Frank Henigman <fjhenigman@chromium.org>