Manage every node and npm version pin in contributors-gitlab-com

Why

Follow up to gitlab-org/developer-relations/contributor-success/contributors-gitlab-com#489 (closed)

contributors-gitlab-com pins node and npm in several files. Renovate only reads contributors/package.json, so every bump lands half done and a maintainer finishes it by hand.

The last npm update shows it. In gitlab-org/developer-relations/contributor-success/contributors-gitlab-com!2629 (merged):

Commit	Author	Files
6a39cbd4 Update npm to v12	GitLab Renovate Bot	contributors/package.json
3e71b33c Bump remaining places	Lee Tickett (maintainer)	.gitlab-ci.yml, .tool-versions, docker/dev.Dockerfile, contributors/package-lock.json

What

Enable mise so mise.toml is read, and add 4 custom managers for the copies. The mise manager only resolves node and ruby, so the npm and lefthook lines of that file are covered by regex like the other copies.

File	Pin
.gitlab-ci.yml, docker/dev.Dockerfile	NODE_VERSION
mise.toml, .gitlab-ci.yml, docker/dev.Dockerfile	npm, NPM_VERSION
contributors/package-lock.json	the engines.npm mirror
mise.toml, docker/dev.Dockerfile	lefthook, ARG LEFTHOOK_VERSION