feat(integrations): Save action message for issues

[ykamo001]

Add repository into Issue Alert code path to start being able to use it, and create the FF that we will use to enable the logic.

Requires: #66623

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 83.49%. Comparing base (7547479) to head (c5fd7a4).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #66626      +/-   ##
==========================================
- Coverage   84.30%   83.49%   -0.82%     
==========================================
  Files        5307     5307              
  Lines      237218   237220       +2     
  Branches    41027    41028       +1     
==========================================
- Hits       199975   198055    -1920     
- Misses      37024    38946    +1922     
  Partials      219      219              

Files	Coverage Δ
src/sentry/conf/server.py	89.61% <ø> (ø)
src/sentry/features/__init__.py	100.00% <100.00%> (ø)
src/sentry/integrations/repository/__init__.py	100.00% <100.00%> (ø)
.../sentry/integrations/slack/actions/notification.py	87.36% <100.00%> (+0.41%)	⬆️

... and 219 files with indirect coverage changes