MM-49564: Drafts upsert in the Store vs App layer (#22530)

* MM-49564: Upsert in the Store vs App layer

Refactor drafts so that Upserting a draft would happen in the DB and not
in the app layer.

* Fixes mocks

* Fixes tests

* Fixes translations

* Fixes tests

* Update tests

* Fixes tests

* Addresses review comments

- renames Save => Upsert
- removes Sleep from tests

* Fixes flaky test

---------

Co-authored-by: Mattermost Build <build@mattermost.com>

server/i18n/en.json

@@ -5027,10 +5027,6 @@
     "id": "app.draft.save.app_error",
     "translation": "Unable to save the Draft."
   },
-  {
-    "id": "app.draft.update.app_error",
-    "translation": "Unable to update the Draft."
-  },
   {
     "id": "app.email.no_rate_limiter.app_error",
     "translation": "Rate limiter is not set up."