Use vkCmd*DebugUtilsLabelEXT() calls to delimit all GLES commands, and
group them under GLES draw/dispatch calls.  Plumb calls from the EVENT
macro (for every GL entrypoint) to vkCmd*DebugUtilsLabelEXT() via a
newly-implemented DebugAnnotatorVk class.  Use a new dirty bit so that
cached entrypoints are associated with a triggering draw/dispatch
command.

The DebugAnnotatorVk::beginEvent() method saves a string in a vector
of all GL commands in ContextVk.  The dirty bit converts the strings
into begin-end vkCmd*DebugUtilsLabelEXT() pairs.  The
DebugAnnotatorVk::endEvent() method makes the final
vkCmdEndDebugUtilsLabelEXT() call for a draw/dispatch command.

Enable the OGL->VK mapping feature by setting
"angle_enable_trace = true" in GN args.

Bug: b/162068318
Bug: b/169243237
Change-Id: I61b6a8d113168c0ce578d6efd002d8a393659aba
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2451517Reviewed-by: Courtney Goeltzenleuchter <courtneygo@google.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Ian Elliott <ianelliott@google.com>