Enforce tests don't change files in source tree

[zeripath]

As discussed in #9515 we can add a make test-check statement to ensure that files in the source-tree are not changed following make test or make unit-test-coverage.

[sapk]

It feel a little bit too verbose compared to other make command and I don't think that the color use is supported in all shell but it could be merged as it is and change later.

[codecov-io]

Codecov Report

Merging #9625 into master will decrease coverage by 0.01%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           master    #9625      +/-   ##
==========================================
- Coverage   42.27%   42.25%   -0.02%     
==========================================
  Files         610      610              
  Lines       80370    80372       +2     
==========================================
- Hits        33974    33964      -10     
- Misses      42217    42229      +12     
  Partials     4179     4179

Impacted Files	Coverage Δ
models/list_options.go	57.89% <ø> (ø)	⬆️
routers/org/members.go	0% <0%> (ø)	⬆️
routers/repo/commit.go	29.66% <0%> (-0.26%)	⬇️
services/pull/patch.go	62.89% <0%> (-3.15%)	⬇️
models/unit.go	37.03% <0%> (-2.47%)	⬇️
services/pull/check.go	56.64% <0%> (-2.1%)	⬇️
models/error.go	30.76% <0%> (-0.55%)	⬇️
modules/avatar/avatar.go	54% <0%> (+6%)	⬆️

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