Update SkOpts namespaces.

If we make sure all SkOpts functions are static, we can give the namespaces any
name we like.  This lets us drop the sk_ prefix and give a real indication of
the default SIMD instruction set rather than just saying sk_default.

Both of these changes help debugger, profiler, and crash report readability.
Perhaps more importantly, keeping these functions static helps prevent
accidentally linking in unused versions of functions, as you see here with
sk_avx::srcover_srgb_srgb().

This requires we update SkBlend_opts tests and benches to call SkOpts functions
through SkOpts rather than declaring the methods externally.  In practice this
drops testing of the SSE2 version on machines with SSE4.  If we still really
need to test/bench the compile time best SIMD level version of this method
against the runtime detected best, we can include SkBlend_opts.h into the tests
or benches directly, similar to what we do for the trivial, brute-force, or best
non-SIMD versions.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2145833002
CQ_INCLUDE_TRYBOTS=client.skia:Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Release-SKNX_NO_SIMD-Trybot

Review-Url: https://codereview.chromium.org/2145833002
9 files changed