Fix Regex Character Class Escape Tests

[Aurele-Barriere]

This PR is the follow-up of PR 4195.

Auto-generated tests for character class escapes are not testing what they should.
This commit modifies their generator so that we check, for each character class escape that it matches exactly the characters it's supposed to match, not more and not less.

[ptomato]

For future reference — when I cleaned up the original test generator I removed this file that modified the regenerate library's object prototype, and instead I turned it into regular functions in index.mjs. I would like to try to minimize the diff in this PR so that it's easier to see what changed, so I've taken the liberty of editing these functions so they don't modify the regenerate prototype and moving them back to index.mjs.

[ptomato]

@Aurele-Barriere Sorry, I did something that closed this PR by accident when I updated it. I can't reopen it for some reason. Would you mind reopening it?

In any case, I apologize for leaving it for so long.

[Aurele-Barriere]

Hi, no worries, here it is again: #4423

[ljharb]

@ptomato actually you pushed this PR to main, effectively merging it.

[ljharb]

I've just force-pushed those changes out (48bb262 was the head).

[Aurele-Barriere]

@ptomato actually you pushed this PR to main, effectively merging it.

If I understand correctly, I don't think this PR has been merged to main, my changes are not in the current files of the main branch of test262 (the regex character class escapes tests are still inadequate).
However, recent test262 commits have been force-pushed to my fork (https://github.com/Aurele-Barriere/test262/tree/main), so I think my changes were deleted by the force-push.
I think it is fine to resume the review from the new pull request, #4423 , created from a new fork

[ljharb]

@Aurele-Barriere that's because i just force-pushed them out :-) there's no choice but to resume from the new pull request, so that's fine.