SSE optimizations for GrayAlpha -> RGBA/BGRA Premul/Unpremul

SSE optimizations for GrayAlpha -> RGBA/BGRA Premul/Unpremul

Swizzle Runtime (Dell Venue 8)
Unpremul 0.17x
Premul   0.20x

PNG Decode Runtime on GrayAlpha Encoded PNGs (Dell Venue 8)
Unpremul Regular  0.91x
Unpremul ZeroInit 0.92x
Premul   Regular  0.84x
Premul   ZeroInit 0.85x

BUG=skia:4767
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1666853002
CQ_EXTRA_TRYBOTS=client.skia:Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Release-SKNX_NO_SIMD-Trybot

Review URL: https://codereview.chromium.org/1666853002