Remove libs/regex_to_circom

[saleel]

Description

Remove libs/regex_to_circom in favour of zk-regex
Git maintains the history in case needed. URL

Type of Change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist:

• I have discussed with the team prior to submitting this PR
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings
• New and existing unit tests pass locally with my changes

[Divide-By-0]

I think there's a few mentions left in the readmes?

[saleel]

They are commented out in the docs.
I have removed them anyway.

[Divide-By-0]

Good to merge after resolving merge conflicts!