CL/VK: Add rewrite-packed-structs and int8 CLSPV option To support structs with three- and four-component vectors, --rewrite-packed-structs is needed as a CLSPV option. The --int8 option is added to allow shaders to process char buffers. Tests-Passing: OCLCTS.test_vectors vec_align_packed_struct_arr Bug: angleproject:397733768 Change-Id: I98ecc9e82bc599453c27f60737bde752c69decd4 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/6284137 Reviewed-by: Austin Annestrand <a.annestrand@samsung.com> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>