This PR introduces a new shared regex pack containing various shared code that analyze regular expressions.
All these analyses depend on a single RegexTreeViewSig signature, that describes a regex as a tree structure.

I don't expect that a shared regex parser will ever make it into this pack.

This is just the shared pack, there are separate PRs that will integrate this shared pack with each language (see bottom).
A complete PR, that combines all the part, can be found here: #10604 (ugly commit history).

I ended up basing locations on hasLocationInfo as not all languages had Location objects for all the regex terms.
This also required some small rewrites in the implementation.

The class hierarchy inside RegexTreeViewSig was needed in order to have some hierarchy that all the languages could agree on, and that's why I had to introduce a Top class.
(RegExpParent has a slightly different hierarchy in JS).

This PR should only be merged when a stable CLI supports all the required features, and when all the major core bugs have been fixed.

I've made separate PRs that port each language to the shared pack:
JavaScript, Ruby, Python, Java.

TODO:

• port ReDoS: fix canonicalization in NfaUtils #11071 into the shared pack
• change to reflect changes in Use ${workspace} for intra-workspace dependencies #11004