Vulkan: 8bit index support for DrawElementsIndirect Add partial support for DrawElementsIndirect. This supports all primitives types except lineloop. Includes a compute shader for converting 8bit index buffers to 16bit index buffers where the index buffer range is defined in a GPU buffer. Test: dEQP.GLES31/functional_draw_indirect_* Bug: angleproject:3564 Change-Id: Ibe9c55323e46a398f0b703cd8597a72ba6790570 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1792948 Commit-Queue: Courtney Goeltzenleuchter <courtneygo@google.com> Reviewed-by: Jamie Madill <jmadill@chromium.org>