This initial prototype introduces a new feature to the Vulkan back-end
that disables the deferred command recording. The intent is to have a
lower CPU overhead during submission calls which currently walk a DAG.

The feature is not complete. Currently it only passes the ANGLE
SimpleOperationTests. Moreover it is extremely simple and only allows
use of one command buffer at a time. In the future we'll allow open
command buffers for recording outside and inside render pass commands
at the same time. We'll also support collapsing RenderPasses together
for some use cases.

Currently the prototype only passes "SimpleOperationTest". There are
quite a few unimplemented features like queries, XFB, etc.

Bug: angleproject:4029
Change-Id: I82760986683f55e37ac4ea559de6f4cffb6ef84e
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1953485
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Tobin Ehlis <tobine@google.com>