The main component of this change is to make vk::BufferHelper,
vk::ImageHelper and vk::SyncHelper use a common path. We introduce a
new "vk::SharedGarbage" helper class that stores small lists of garbage
from individual objects like an ImageHelper or BufferHelper. The
SharedGarbage is stored in the RendererVk with the ResourceUse of the
helper object. The ResourceUse tells RendererVk when it is safe to
destroy the GarbageObjects.

New "onGraphAccess" commands are added in a few places to enable the
common garbage collection path. A couple Context-only resources like
default attributes now are referenced where they were not before.

Also reorganizes some functions so we can add a few helpful ASSERTs
to our graph dependencies. Added "updateCurrentAccessNodes" for this.

Also adds a "RendererScoped" helper to replace many uses of
"ContextScoped".

The multithreading EGL tests mostly pass but have some remaining
flakiness so cannot yet be enabled.

Bug: angleproject:2464
Change-Id: Ia3e3ae8848d731abf3f21ebe04c33e381e130be0
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1808444
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>