vkCmdPipelineBarrier call

Nvidia preferes one barrier call than multiple calls with fine grained
stage dependency information. They do not care much about stage
dependency. This adds a feature flag that sets to true on nvidia and
will merge all barriers into one call.

Bug: angleproject:4633
Change-Id: I204484aa4c5989655f74d70a0eaa235c3c83f548
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2207635
Commit-Queue: Charlie Lao <cclao@google.com>
Reviewed-by: Courtney Goeltzenleuchter <courtneygo@google.com>