[WEB - 467] perf: issues listing endpoints (#3710)

* dev: update issue listing apis

* dev: optimize issue listing apis

* fix: sub issues endpoint

* add loading state for subscription in issueDetail

* fix: import error

---------

Co-authored-by: rahulramesha <rahulramesham@gmail.com>

apiserver/plane/app/urls/issue.py

@@ -90,11 +90,13 @@ urlpatterns = [
         BulkImportIssuesEndpoint.as_view(),
         name="project-issues-bulk",
     ),
+    # deprecated endpoint TODO: remove once confirmed
     path(
         "workspaces/<str:slug>/my-issues/",
         UserWorkSpaceIssues.as_view(),
         name="workspace-issues",
     ),
+    ## 
     path(
         "workspaces/<str:slug>/projects/<uuid:project_id>/issues/<uuid:issue_id>/sub-issues/",
         SubIssuesEndpoint.as_view(),