Add support for lineloops.
Includes a compute shader for converting lineloop index
buffer with optional restart into linestrip.

Test:
    dEQP.GLES31/functional_draw_indirect_*
    angle_end2end_tests --gtest_filter=LineLoopIndirectTest.*/*

Bug: angleproject:3564
Change-Id: I12d08db1c8d99867f0611e53be50193647695260
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1797106
Commit-Queue: Courtney Goeltzenleuchter <courtneygo@google.com>
Reviewed-by: Tobin Ehlis <tobine@google.com>