Bump `bitflags` to v2 (#400) #654

Job	Run time
powerpc_cross	9s
test_all (ubuntu-latest)	3m 11s
feature_check (ubuntu-latest)	59s
test_all (macos-latest)	2m 32s
build (1.57.0, ubuntu-latest)	1m 22s
feature_check (macos-latest)	38s
rustfmt	4s
build (1.57.0, windows-latest)	1m 44s
feature_check (unstable, ubuntu-latest)	1m 0s
build (1.57.0, macos-latest)	1m 24s
feature_check (unstable, macos-latest)	31s
feature_check (benchmarks, ubuntu-latest)	58s
build (stable, ubuntu-latest)	6s
build (stable, windows-latest)	55s
feature_check (benchmarks, macos-latest)	31s
build (stable, macos-latest)	10s
build (beta, ubuntu-latest)	14s
build (beta, windows-latest)	30s
build (beta, macos-latest)	20s
build (nightly, ubuntu-latest)	14s
build (nightly, windows-latest)	35s
build (nightly, macos-latest)	16s
	18m 23s

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