Support unprotected file patterns

[jpraet]

Fixes #16381.

Note that changes to unprotected files via the web editor still cannot be pushed directly to the protected branch.
I could easily add such support for edits and deletes if needed. But for adding, uploading or renaming unprotected files, it is not trivial.

[codecov-commenter]

Codecov Report

Merging #16395 (3a2572e) into main (77f604a) will increase coverage by 0.03%.
The diff coverage is 40.83%.

@@            Coverage Diff             @@
##             main   #16395      +/-   ##
==========================================
+ Coverage   45.21%   45.24%   +0.03%     
==========================================
  Files         766      766              
  Lines       86596    86641      +45     
==========================================
+ Hits        39154    39204      +50     
+ Misses      41103    41093      -10     
- Partials     6339     6344       +5     

Impacted Files	Coverage Δ
modules/repofiles/delete.go	56.04% <0.00%> (+7.42%)	⬆️
services/auth/source/ldap/source_search.go	46.81% <0.00%> (ø)
services/forms/repo_form.go	41.25% <ø> (ø)
modules/repofiles/update.go	37.20% <11.11%> (-0.67%)	⬇️
models/branches.go	44.33% <29.41%> (-0.39%)	⬇️
services/pull/patch.go	61.27% <35.71%> (+7.03%)	⬆️
routers/private/hook.go	34.68% <45.45%> (+0.23%)	⬆️
modules/git/diff.go	75.26% <75.00%> (-0.05%)	⬇️
modules/convert/convert.go	79.66% <100.00%> (+0.08%)	⬆️
routers/api/v1/repo/branch.go	38.75% <100.00%> (+0.50%)	⬆️
... and 10 more

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