Display ui time with customize time location (#7792)

* display ui time with customize time location

* fix lint

* rename UILocation to DefaultUILocation

* move time related functions to modules/timeutil

* fix tests

* fix tests

* fix build

* fix swagger

templates/swagger/v1_json.tmpl

@@ -9770,7 +9770,7 @@
       "description": "TimeStamp defines a timestamp",
       "type": "integer",
       "format": "int64",
-      "x-go-package": "code.gitea.io/gitea/modules/util"
+      "x-go-package": "code.gitea.io/gitea/modules/timeutil"
     },
     "TrackedTime": {
       "description": "TrackedTime worked time for an issue / pr",