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>

Makefile

@@ -451,7 +451,7 @@ $(GO_LICENSE_FILE): go.mod go.sum
 	GO=$(GO) $(GO) run build/generate-go-licenses.go $(GO_LICENSE_FILE)
 
 .PHONY: test-integration
-test-integration:
+test-integration: $(EXECUTABLE)
 	@# Use a compiled binary: testlogger forwards gitea logs to t.Log, so `go test -v`
 	@# would flood output per passing test. testcache can't help these tests anyway —
 	@# they mutate the work directory, so cache inputs change between runs.
@@ -463,7 +463,7 @@ test-integration-compile:
 	$(GO) test $(GOTEST_FLAGS) -tags '$(TAGS)' -c -o /dev/null gitea.dev/tests/integration
 
 .PHONY: test-integration\#%
-test-integration\#%:
+test-integration\#%: $(EXECUTABLE)
 	$(GO) test $(GOTEST_FLAGS) -tags '$(TAGS)' -run $(subst .,/,$*) gitea.dev/tests/integration
 
 .PHONY: test-migration