transition `Permissions` from `u64` to `SmolBitSet` #6397

Job	Run time
Build docs	57s
Check (builder without model)	37s
Check (unstable + typesize)	56s
Check (temp cache + typesize)	1m 1s
Check (unstable (no default features))	42s
Check minimal versions	46s
Check (temp cache)	59s
MSRV	-1s
Examples	3m 7s
Test (stable)	1m 25s
Test (Windows)	3m 43s
Test (beta)	1m 31s
Test (nightly)	1m 20s
Test (macOS)	2m 38s
Test (chrono)	41s
Test (no gateway)	1m 9s
Test (native-tls)	1m 31s
Test (zlib compression)	1m 21s
Test (zlib and zstd compression)	1m 27s
Test (zstd compression)	1m 29s
Test (no default features)	42s
Test (no cache)	1m 20s
	29m 21s

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