fix: update regex engine to support possessive match and lookbehind syntaxes

[cmmoran]

Update the regexp to conditionally (naively?) change the current start,end delimiters for the regexp from the hard-coded '<','>' to '{','}' when the compiler encounters a pattern that has syntax that includes '(?<' or '(?>' organically.

BREAKING CHANGES: None

Related issue(s)

Relates:
#441

Fixes:
#1089

Checklist

• I have read the contributing guidelines.
• I have referenced an issue containing the design document if my change
  introduces a new feature.
• I am following the
  contributing code guidelines.
• I have read the security policy.
• I confirm that this pull request does not address a security
  vulnerability. If this pull request addresses a security vulnerability, I
  confirm that I got the approval (please contact
  [email protected]) from the maintainers to push
  the changes.
• I have added tests that prove my fix is effective or that my feature
  works.
• I have added or changed the documentation.

Further Comments

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.88%. Comparing base (8fc9b7a) to head (ae8fb6e).
Report is 7 commits behind head on master.

❗ Current head ae8fb6e differs from pull request most recent head e3e9566

Please upload reports for the commit e3e9566 to get more accurate results.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1147      +/-   ##
==========================================
- Coverage   77.90%   77.88%   -0.03%     
==========================================
  Files          80       80              
  Lines        3929     4047     +118     
==========================================
+ Hits         3061     3152      +91     
- Misses        595      616      +21     
- Partials      273      279       +6     

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[aeneasr]

Thank you for the changes, however the reason lookbehind is not working is because we're using the golang std library, which does not support these features.

[aeneasr]

I'm actually wrong, looksl ike this is working, which is very nice!