[API] ListIssues add filter for milestones (#10148)

* Refactor Issue Filter Func

* ListIssues add filter for milestones

* as per @lafriks

* documentation ...

templates/swagger/v1_json.tmpl

@@ -3768,6 +3768,12 @@
             "name": "type",
             "in": "query"
           },
+          {
+            "type": "string",
+            "description": "comma separated list of milestone names or ids. It uses names and fall back to ids. Fetch only issues that have any of this milestones. Non existent milestones are discarded",
+            "name": "milestones",
+            "in": "query"
+          },
           {
             "type": "integer",
             "description": "page number of results to return (1-based)",