feat(analytics): Implement semver and date custom ops for flags runtime props

[efahk]

Adds Semantic Versioning and RFC3339 date comparison support for feature flags runtime event matching. This implements them as extensions to the JSONLogic library that is being used for targeting.

See here for more information about the comparators and golden vector list

[greptile-apps]

Confidence Score: 3/5

The PR is not yet safe to merge because the two previously reported comparison defects remain reachable and can select incorrect flag variants.

Datetime operands still lose sub-second precision, and runtime-rule preprocessing still case-folds SemVer prerelease identifiers before their case-sensitive comparison.

Files Needing Attention: mixpanel/flags/custom_operators.py, mixpanel/flags/local_feature_flags.py

Important Files Changed

Filename	Overview
mixpanel/flags/custom_operators.py	Implements both comparators, but datetime conversion still truncates millisecond precision.
mixpanel/flags/local_feature_flags.py	Registers the operators, while existing case folding still corrupts case-sensitive SemVer prerelease comparisons.
mixpanel/flags/test_custom_operators.py	Exercises operator registration, golden vectors, malformed operands, and invalid datetime targets.
pyproject.toml	Adds python-dateutil and packages the golden-vector fixtures.

_{Reviews (5): Last reviewed commit: "date updates" | Re-trigger Greptile}

[codecov]

Codecov Report

❌ Patch coverage is 98.13953% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 96.39%. Comparing base (176d855) to head (4b5af32).

Files with missing lines	Patch %	Lines
mixpanel/flags/custom_operators.py	97.05%	3 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #193      +/-   ##
==========================================
+ Coverage   96.25%   96.39%   +0.14%     
==========================================
  Files          13       15       +2     
  Lines        2616     2831     +215     
  Branches      139      174      +35     
==========================================
+ Hits         2518     2729     +211     
- Misses         64       67       +3     
- Partials       34       35       +1     

Flag	Coverage Δ
openfeature-provider	50.89% <21.89%> (-3.17%)	⬇️

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