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/rooms/BasicMessageComposer.tsx

@@ -789,6 +789,7 @@ export default class BasicMessageEditor extends React.Component<IProps, IState>
                 aria-activedescendant={activeDescendant}
                 dir="auto"
                 aria-disabled={this.props.disabled}
+                data-testid="basicmessagecomposer"
             />
         </div>);
     }