Vulkan: Implement debug markers Covers both GL_KHR_debug and GL_EXT_debug_marker. Debug markers are used to specify events or hierarchically categorize a set of commands within the command buffer. When debugging, this allows for quicker navigation to the draw calls of interest, and otherwise provides context to debug output. Bug: angleproject:2853 Change-Id: Id65e11fc877d9e70b6fd0fae7f0bbbcb1164bf10 Reviewed-on: https://chromium-review.googlesource.com/c/1403956 Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org>