Compute dispatch commands must be submitted outside a renderpass,
but their associated debug event markers were being submitted
on the renderpass commandbuffer. The dispatch debug event markers are
now handled separately from those for draw calls and are now submitted
on the correct commandbuffer.

Failure manifested in malformed AGI traces for Ragnarok M:
Eternal Love

Bug: b/181611786
Change-Id: I768eeccd76be38818fc99d6d56f5899290c8fc5b
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2930818Reviewed-by: Ian Elliott <ianelliott@google.com>
Reviewed-by: Cody Northrop <cnorthrop@google.com>
Commit-Queue: Ian Elliott <ianelliott@google.com>