Introduce `rusty-cachier` (#11462)

* Introduce `rusty-cachier`

* Return LF at the end of file

* Use `entrypoint` to `unshare(1)` into a new mount namespace

* Use `rusty-cachier`-provided absolute path for `CARGO_TARGET_DIR` everywhere

* Debug single `build-rustdoc` job

* CI: debug

* CI: debug

* CI: debug

* `unshare(1)` is no longer needed

* CI: remove debug

* Revert "Debug single `build-rustdoc` job"

* Formatiing

* Update scripts/ci/gitlab/pipeline/build.yml

Co-authored-by: Denis Pisarev <[email protected]>