test: speed up tests, fix transaction bug (#39030)

Speed up tests: `make test-backend` 103s to 37s, `make test-integration`
908s to 852s.

Most of it is a detached system notice insert blocking on the SQLite
write lock until the busy timeout expired, and `ExternalServiceHTTP`
re-probing on every call with an untimed `http.Get`.

- fixed one correctness bug with nested transactions: files were deleted
while the outer transaction was open, so a later failure could roll the
database back with the files gone
- git push branch counts were far above the hook batch size
- Fix makefile dependencies so running tests and lint work in fresh
worktrees.

---------

Co-authored-by: Giteabot <teabot@gitea.io>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

.github/workflows/pull-compliance.yml

@@ -24,8 +24,7 @@ jobs:
         with:
           lint-cache: "true"
       - run: make deps-backend deps-tools
-      - run: TAGS="bindata" make generate-go # lint-go also lints with "bindata" tags which requires "_bindata.go"
-      - run: make lint-backend
+      - run: TAGS="bindata" make generate-go lint-backend # lint-go can lint with "bindata" tags
 
   lint-on-demand:
     needs: files-changed