implement bls12-381 functions #4262

Job	Run time
build-fuzz	2m 58s
check-git-rev-deps	11s
build-and-test (msrv, ubuntu-latest, x86_64-unknown-linux-gnu)	8m 2s
cargo-deny (advisories)	49s
build-and-test (msrv, ubuntu-latest, aarch64-unknown-linux-gnu, true)	4m 51s
cargo-deny (bans licenses sources)	50s
build-and-test (msrv, windows-latest, x86_64-pc-windows-msvc)	18m 38s
fmt	5s
docs	4m 41s
build-and-test (latest, ubuntu-latest, x86_64-unknown-linux-gnu)	8m 4s
build-and-test (latest, ubuntu-latest, aarch64-unknown-linux-gnu, true)	4m 40s
publish-dry-run	0s
readme	2m 47s
build-and-test (latest, windows-latest, x86_64-pc-windows-msvc)	18m 5s
semver-checks	6m 2s
complete	1s
	1h 20m 44s

Provide feedback