Prepare and check test env during CI

[wxiaoguang]

This PR should resolve the permission problems during CI, if the uid doesn't match, a more clear message is shown.

• CI fails with unknown permission problems #17710

The new drone step dependencies:

(root)prepare-test-env -> (gitea)build -> (gitea)test

[codecov-commenter]

Codecov Report

Merging #17725 (c8f467a) into main (a85e75b) will increase coverage by 0.01%.
The diff coverage is n/a.

❗ Current head c8f467a differs from pull request most recent head 10c678d. Consider uploading reports for the commit 10c678d to get more accurate results

@@            Coverage Diff             @@
##             main   #17725      +/-   ##
==========================================
+ Coverage   45.44%   45.46%   +0.01%     
==========================================
  Files         802      802              
  Lines       89233    89235       +2     
==========================================
+ Hits        40556    40571      +15     
+ Misses      42140    42128      -12     
+ Partials     6537     6536       -1     

Impacted Files	Coverage Δ
modules/charset/charset.go	71.71% <0.00%> (-6.07%)	⬇️
modules/process/manager.go	72.83% <0.00%> (-2.47%)	⬇️
services/gitdiff/gitdiff.go	73.98% <0.00%> (-0.89%)	⬇️
routers/api/v1/repo/pull.go	28.83% <0.00%> (-0.52%)	⬇️
services/pull/pull.go	42.19% <0.00%> (+0.40%)	⬆️
models/issue_comment.go	52.77% <0.00%> (+0.56%)	⬆️
models/repo_list.go	79.21% <0.00%> (+0.78%)	⬆️
models/notification.go	65.58% <0.00%> (+0.86%)	⬆️
models/project_issue.go	29.90% <0.00%> (+1.33%)	⬆️
modules/notification/ui/ui.go	62.31% <0.00%> (+1.44%)	⬆️
... and 4 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 96ec656...10c678d. Read the comment docs.