[MM-25647]: ability to permanently delete users (#14944)

Summary:
    Config option to allow permanent user deletion ServiceSettings.EnableAPIUserDeletion
    Expose permanent user deletion through API
    Local mode for delete user for use in mmctl

Ticket Link:
    Server part of https://mattermost.atlassian.net/browse/MM-25647

i18n/en.json

@@ -2622,6 +2622,10 @@
     "id": "api.user.delete_team.not_enabled.app_error",
     "translation": "Permanent team deletion feature is not enabled. Please contact your System Administrator."
   },
+  {
+    "id": "api.user.delete_user.not_enabled.app_error",
+    "translation": "Permanent user deletion feature is not enabled. Please contact your System Administrator."
+  },
   {
     "id": "api.user.demote_user_to_guest.already_guest.app_error",
     "translation": "Unable to convert the user to guest because is already a guest."