chore: noir subrepo experiment (WIP, do not merge)

[ludamad]

Description

What if we used a git subrepo bundled copy of noir-lang/noir?

This would allow prototyping changes from within aztec entirely if we need to do full stack changes, and then making a noir PR as needed with git subrepo push noir <branch>. We can periodically git subrepo pull noir <branch> as well.

This does NOT copy Noir history, and this tool condenses history every pull. Noir repo is the source of history.
This does NOT monorepo Noir, although the source is bundled. The intent is that PR's can get reviewed by Noir folks in aztec-packages, but they should always still make their way as separate Noir PR's.

Alternatives: git subtree (most similar, keeps history however), git submodules (I feel like sentiment is: stay away), monorepoing Noir (personally in favour, but probably the most reasonable split if there is one as well + obviously not Noir's ideal end state)

Checklist:

• [No, sorry] I have reviewed my diff in github, line by line.
• [*] Every change is related to the PR description.
• [*] I have linked this pull request to the issue(s) that it resolves.
• [*] There are no unexpected formatting changes, superfluous debug logs, or commented-out code.
• [*] The branch has been merged or rebased against the head of its merge target.
• [No] I'm happy for the PR to be merged at the reviewer's next convenience.

[ludamad]

Clearing currently inactive PRs.