Bump `bitflags` to v2 (#400) #653

Job	Run time
powerpc_cross	8s
rustfmt	8s
build (1.57.0, ubuntu-latest)	1m 4s
feature_check	1m 0s
build (1.57.0, windows-latest)	1m 51s
test_all	3m 1s
feature_check (benchmarks)	1m 0s
build (1.57.0, macos-latest)	1m 13s
build (stable, ubuntu-latest)	11s
build (stable, windows-latest)	49s
build (stable, macos-latest)	9s
build (beta, ubuntu-latest)	13s
build (beta, windows-latest)	36s
build (beta, macos-latest)	16s
build (nightly, ubuntu-latest)	12s
build (nightly, windows-latest)	41s
build (nightly, macos-latest)	16s
	12m 48s

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