Vulkan: lineloop support for DrawArrayIndirect Add support for lineloops. Includes a compute shader for generating an index buffer to draw lineloop. Instancing turns out to be a special case for indirect draws if we have vertex attributes that need to be emulated (e.g. divisor too large or native vertex format not available). Test: dEQP.GLES31/functional_draw_indirect_* angle_end2end_tests --gtest_filter=LineLoopIndirectTest.*/* dEQP.GLES3/functional_draw_* Bug: angleproject:3564 Change-Id: I1fdabe2c8a690c8b6df9e252e1e839e08796bcca Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1834682 Commit-Queue: Courtney Goeltzenleuchter <courtneygo@google.com> Reviewed-by: Geoff Lang <geofflang@chromium.org>