Rename Layout to LayoutBitset #577

Job	Run time
nostd/thumbv6m-none-eabi/stable	19s
Pass MSRV values to other jobs	2s
format/nightly	14s
miri	10m 59s
cross_test/i686-unknown-linux-gnu/stable	36s
cross_test/s390x-unknown-linux-gnu/stable	37s
cargo-careful	55s
docs/nightly	19s
clippy/stable	24s
tests/1.64.0	1m 15s
tests/beta	1m 3s
tests/stable	1m 0s
blas-msrv	47s
tests/nightly	1m 0s
conclusion	-1s
	19m 29s

Provide feedback