feat(bitfield): add `u128` support #1313

Job	Run time
changed_paths	9s
build boot image (x86_64)	7m 6s
cargo check (host)	7m 48s
Loom tests (cordyceps)	5m 29s
clippy	6m 59s
Miri tests (codyceps)	6m 32s
docs	8m 38s
Loom tests (maitake)	8m 9s
Tests (maitake, no-default-features)	5m 40s
rustfmt	13s
cargo test (host)	8m 48s
cargo test (cross x64)	8m 14s
Loom tests (mycelium-util)	4m 43s
	1h 18m 28s

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