It can be hard to tell sometimes when the mRenderPassCommands or
mOutSideRenderPassCommands command buffers have changed and there have
been some issues with code that locally caches a pointer to a
commandBuffer that then becomes invalid.
This change adds checking so that if a command is being added to a
commandBuffer that's been closed (e.g. submitted for processing) then we
hit an assert.

Bug: b/168144059
Change-Id: If5d37c462e3bcb51f6ec2ca44c27a2fad4e57c19
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2405812Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Tim Van Patten <timvp@google.com>
Commit-Queue: Courtney Goeltzenleuchter <courtneygo@google.com>