starter procs for blending with pm4f

curr/maxrss	loops	min	median	mean	max	stddev	samples   	config	bench
   8/8   MB	4	87.1µs	91µs	89.8µs	92µs	2%	▇▇▇▇█▇▅▁▁▁	nonrendering	xfer4f_srcover_N_opaque_linear
   9/9   MB	2	196µs	196µs	215µs	383µs	27%	▁▁▁▁█▁▁▁▁▁	nonrendering	xfer4f_srcover_N_opaque_srgb
   9/9   MB	1	313µs	313µs	313µs	313µs	0%	▁▄▅▅▅▂████	nonrendering	xfer4f_srcover_N_alpha_linear
   9/9   MB	1	580µs	580µs	582µs	602µs	1%	▁▁▁▁▁▁▂▁▁█	nonrendering	xfer4f_srcover_N_alpha_srgb
   9/9   MB	23	13.1µs	13.1µs	13.1µs	13.1µs	0%	▆▄▄█▂▂▂▁▂▁	nonrendering	xfer4f_srcover_1_opaque_linear
   9/9   MB	23	13.2µs	13.2µs	13.2µs	13.2µs	0%	█▄▂▁▃▁▂▂▂▂	nonrendering	xfer4f_srcover_1_opaque_srgb
   9/9   MB	2	178µs	183µs	183µs	185µs	1%	▇▇▇█▇▇▇▇▇▁	nonrendering	xfer4f_srcover_1_alpha_linear
   9/9   MB	1	517µs	517µs	517µs	517µs	0%	▇█▄▃▄▁▂▁▂▄	nonrendering	xfer4f_srcover_1_alpha_srgb

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1642703003

TBR=
landing now so these incremental types/functions can be used to collaborate with herb's work. nothing is active at this point

Review URL: https://codereview.chromium.org/1642703003
8 files changed