[clang-tools-extra] Enforce SL.con.3: Add check to replace operator[] with at() (PR #90043)

[Paul Heidekrüger via cfe-commits]

PBHDK wrote:

> > > I am adding @leunam99 and @PBHDK to the PR, who will contribute in the next few weeks.
> > 
> > 
> > Since we cannot push to this PR, we will be submitting a new PR with @sebwolf-de's + our work, correct, @EugeneZelenko, @PiotrZSL, @HerrCai0907?
> 
> Could you please resolve conversations for fixed comments?

Once we're clear on all our questions (see comments above), we'll submit a new PR that'll resolve all comments.
The code is ready, but we don't want to submit the PR as long as we still have open questions.
The problem is that we can't mark them as resolved on GitHub ourselves, and Sebastian is out-of-office right now.

I don't know if you can assign us to this PR somehow, but if not, someone else would have to mark them as resolved.

https://github.com/llvm/llvm-project/pull/90043