Fix threads fallback incorrectly targets root event (#9229)

* Use RelationType enum instead of hardcoded value

* Fix threads replies fallback to target last reply

* Only unsubscribe from threads events if needed

* fix strict null check

* fix strict null checks

* strict null checks

* fix typing

* Unsubscribe listeners if new thread is `null`

Co-authored-by: Faye Duxovni <fayed@element.io>

* Update strict null checks

* Type HTMLElement as nullable

* Add thread fallback integration test

* lint fix

* Update snapshots

* Add test after changing thread

* Remove test comment

* update snapshot

* fix room context test utility

* Add ThreadListContextMenu test

* lint fix

* fix thread rendering

Co-authored-by: Faye Duxovni <fayed@element.io>
Co-authored-by: Michael Telatynski <7t3chguy@gmail.com>

src/components/views/elements/Spinner.tsx

@@ -40,6 +40,7 @@ export default class Spinner extends React.PureComponent<IProps> {
                     style={{ width: w, height: h }}
                     aria-label={_t("Loading...")}
                     role="progressbar"
+                    data-testid="spinner"
                 />
             </div>
         );