Fix sub-command log level (#25537) (#25553)

Backport #25537

More fix for #24981

* #24981

Close #22361, #25552

* #22361
* #25552

There were many patches for Gitea's sub-commands to satisfy the facts:

* Some sub-commands shouldn't output any log, otherwise the git protocol
would be broken
* Sometimes the users want to see "verbose" or "quiet" outputs

That's a longstanding problem, and very fragile. This PR is only a quick
patch for the problem.

In the future, the sub-command system should be refactored to a clear
solution.

----

Other changes:

* Use `ReplaceAllWriters` to replace
`RemoveAllWriters().AddWriters(writer)`, then it's an atomic operation.
* Remove unnecessary `syncLevelInternal` calls, because
`AddWriters/addWritersInternal` already calls it.

modules/log/manager_test.go

@@ -23,7 +23,7 @@ func TestSharedWorker(t *testing.T) {
 	loggerTest := m.GetLogger("test")
 	loggerTest.AddWriters(w)
 	loggerTest.Info("msg-1")
-	loggerTest.RemoveAllWriters() // the shared writer is not closed here
+	loggerTest.ReplaceAllWriters() // the shared writer is not closed here
 	loggerTest.Info("never seen")
 
 	// the shared writer can still be used later