Add invlid value check to DISABLED_REPO_UNITS and fix incorrect slice combine

[yp05327]

If user set incorrect vaule to DISABLED_REPO_UNITS, all invaild items in DisabledRepoUnits will be Unknown Type 0, and there's no process to check the invaild value in this function.

After:

[yp05327]

If there are 2 incorrect values, and the last one in the list is a incorrect value
e.g.

DISABLED_REPO_UNITS = [repo.projects, repo.packages]

we will get an error:

[yp05327]

???

[yp05327]

I don't know whether it is the best way to fix slice combine error in d038707.
But I find there are some same codes:

some of them have same logic.

-> They are correct: #23024 (comment)

[codecov-commenter]

Codecov Report

Merging #23024 (d038707) into main (2b3f12f) will increase coverage by 0.00%.
The diff coverage is 0.00%.

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@@           Coverage Diff           @@
##             main   #23024   +/-   ##
=======================================
  Coverage   47.43%   47.43%           
=======================================
  Files        1139     1140    +1     
  Lines      150707   150790   +83     
=======================================
+ Hits        71491    71532   +41     
- Misses      70755    70788   +33     
- Partials     8461     8470    +9     

Impacted Files	Coverage Δ
models/unit/unit.go	50.38% <0.00%> (-2.00%)	⬇️
modules/util/io.go	73.68% <0.00%> (-21.06%)	⬇️
modules/util/timer.go	85.71% <0.00%> (-14.29%)	⬇️
models/auth/token_scope.go	75.00% <0.00%> (-3.95%)	⬇️
modules/charset/charset.go	71.73% <0.00%> (-3.63%)	⬇️
services/pull/comment.go	62.96% <0.00%> (-2.78%)	⬇️
routers/web/repo/setting_protected_branch.go	33.79% <0.00%> (-1.55%)	⬇️
routers/api/v1/user/app.go	66.26% <0.00%> (-0.71%)	⬇️
modules/setting/server.go	50.90% <0.00%> (-0.47%)	⬇️
services/webhook/notifier.go	55.63% <0.00%> (-0.22%)	⬇️
... and 18 more

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[wxiaoguang]

I guess there is a related PR

• Improve LoadUnitConfig to handle invalid or duplicate units #23736

[wolfogre]

Sorry I overlooked this PR and posted #23736.

Since #23736 also handles DisabledRepoUnits, DefaultRepoUnits, and DefaultForkRepoUnits, @yp05327, what do you think about replacing this one?