Fix 404 and 410 API errors being silently discarded in WebUI (#13279)

* Fix 404 and 410 API errors being silently discarded in WebUI

Fixes #13278

* Return more appropriate error when user replies to a deleted toot

* Please CodeClimate

* Fix 404/410 errors on fetching account timelines & identity proofs

* Refactor error handling

* Move error message string to statuses.errors

app/javascript/mastodon/actions/accounts.js

@@ -396,6 +396,7 @@ export function fetchFollowersFail(id, error) {
     type: FOLLOWERS_FETCH_FAIL,
     id,
     error,
+    skipNotFound: true,
   };
 };
 
@@ -482,6 +483,7 @@ export function fetchFollowingFail(id, error) {
     type: FOLLOWING_FETCH_FAIL,
     id,
     error,
+    skipNotFound: true,
   };
 };
 
@@ -571,6 +573,7 @@ export function fetchRelationshipsFail(error) {
     type: RELATIONSHIPS_FETCH_FAIL,
     error,
     skipLoading: true,
+    skipNotFound: true,
   };
 };