Make gAMA and cHRM fallback optional for sRGB #644

Job	Run time
powerpc_cross	14s
feature_check (ubuntu-latest)	1m 0s
build (1.57.0, ubuntu-latest)	1m 1s
feature_check (macos-latest)	31s
build (1.57.0, windows-latest)	1m 30s
rustfmt	7s
feature_check (unstable, ubuntu-latest)	57s
test_all (ubuntu-latest)	2m 58s
build (1.57.0, macos-latest)	1m 6s
feature_check (unstable, macos-latest)	30s
test_all (macos-latest)	2m 2s
build (stable, ubuntu-latest)	8s
feature_check (benchmarks, ubuntu-latest)	57s
build (stable, windows-latest)	1m 5s
feature_check (benchmarks, macos-latest)	28s
build (stable, macos-latest)	12s
build (beta, ubuntu-latest)	14s
build (beta, windows-latest)	41s
build (beta, macos-latest)	17s
build (nightly, ubuntu-latest)	12s
build (nightly, windows-latest)	44s
build (nightly, macos-latest)	19s
	17m 13s

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