Vulkan: Merge Command Buffer Helpers Merge the outside and inside renderPass command buffer helpers to share the single CommandBufferHelper (CBH) class. This commom class is still used for separate outside and inside renderPass command buffer objects in the context. That's a bit wasteful since some functions and members are only relevant to one type of command buffer. However, this is a foundational change that will provide the immediate benefit of being able to use the CBH as the interface for passing commands to a worker thread. It also provides the long term benefit of starting the refactor to merge the outside and inside renderPass command buffers into a single command buffer object that can be used by the main thread to record all commands whether inside or outside of a renderpass. Bug: b/154030403 Change-Id: I83c63385fe9858bc05853c550d4fb2e13226d582 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2180850 Reviewed-by: Tobin Ehlis <tobine@google.com> Commit-Queue: Tobin Ehlis <tobine@google.com>