build

FR: Add new revset `builtin_immutable_heads()` #13239

Job	Run time
Build jj-lib without Git support	44s
build (ubuntu-latest)	4m 42s
Check protos	36s
build (macos-14)	3m 43s
build (windows-latest)	11m 0s
build (ubuntu-latest, --all-features)	5m 31s
cargo-deny (advisories)	23s
cargo-deny (bans licenses sources)	27s
Clippy check	2m 34s
Check that MkDocs can build the docs	28s
Check that MkDocs can build the docs with Poetry 1.8	32s
Check formatting	17s
	30m 57s

Provide feedback