Regex brain

[DanielNoord]

Steps

• For new features or bug fixes, add a ChangeLog entry describing what your PR does.
• Write a good description on what the PR does.

Description

Supersedes #1929.

Refs #1911

Closes #1911

@smontanaro I wasn't able to push to your branch so I had to create a new PR. This should be enough to get the flags to work.

Type of Changes

	Type
✓	🐛 Bug fix

[coveralls]

Pull Request Test Coverage Report for Build 3824990210

• 19 of 19 (100.0%) changed or added relevant lines in 1 file are covered.
• 63 unchanged lines in 2 files lost coverage.
• Overall coverage increased (+0.02%) to 92.339%

---

Files with Coverage Reduction	New Missed Lines	%
astroid/raw_building.py	18	92.17%
astroid/nodes/node_classes.py	45	94.88%

Totals
Change from base Build 3824117412:	0.02%
Covered Lines:	9956
Relevant Lines:	10782

---

💛 - Coveralls

[smontanaro]

Thanks @DanielNoord. I'm unfamiliar with the astroid code and barely function trying to get patches set up the way the core Python folks want things. It never occurred to me that anyone might want to push anything to my fork. I'm sure I forgot to tweak some setting.

[Pierre-Sassoulas]

LGTM, just adding a little link in the doc.

[DanielNoord]

@Pierre-Sassoulas Do you have a good idea on how to shorten the link?

[DanielNoord]

I'll wait with merging for the codecov PR>

[codecov]

Codecov Report

Merging #1934 (e285714) into main (15d2067) will increase coverage by 0.01%.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1934      +/-   ##
==========================================
+ Coverage   92.56%   92.58%   +0.01%     
==========================================
  Files          92       93       +1     
  Lines       10763    10782      +19     
==========================================
+ Hits         9963     9982      +19     
  Misses        800      800              

Flag	Coverage Δ
linux	92.33% <100.00%> (+0.01%)	⬆️
pypy	88.49% <73.68%> (-0.03%)	⬇️
windows	92.25% <100.00%> (+0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
astroid/brain/brain_regex.py	100.00% <100.00%> (ø)