fix(db): only update fields when necessary for repo hot path writes

[ecrupper]

A few fixes here:

• hook retry loop was not erroring ever because it would always hit the continue in the retry check and move on
• only update repo data if it actually changed (in the webhook hot path). That repo write is useless 99% of the time.
• introduce a PartialRepoUpdate so that concurrent servers are not writing stale counter data ever

[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 39 lines in your changes missing coverage. Please review.
✅ Project coverage is 58.31%. Comparing base (223855d) to head (f6a3d26).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
api/webhook/post.go	0.00%	31 Missing ⚠️
database/repo/create.go	0.00%	2 Missing and 2 partials ⚠️
database/repo/update_partial.go	81.81%	1 Missing and 1 partial ⚠️
scm/github/app_install.go	0.00%	1 Missing ⚠️
scm/github/repo.go	0.00%	1 Missing ⚠️

❌ Your project status has failed because the head coverage (58.31%) is below the target coverage (90.00%). You can increase the head coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1416      +/-   ##
==========================================
- Coverage   58.41%   58.31%   -0.10%     
==========================================
  Files         660      661       +1     
  Lines       25292    25290       -2     
==========================================
- Hits        14774    14748      -26     
- Misses       9833     9854      +21     
- Partials      685      688       +3     

Files with missing lines	Coverage Δ
database/types/repo.go	86.04% <100.00%> (-2.98%)	⬇️
scm/github/app_install.go	0.00% <0.00%> (ø)
scm/github/repo.go	76.17% <0.00%> (ø)
database/repo/update_partial.go	81.81% <81.81%> (ø)
database/repo/create.go	57.14% <0.00%> (-9.53%)	⬇️
api/webhook/post.go	0.00% <0.00%> (ø)

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[wass3rw3rk]

couple of minor things but looks good