Take the Threads Activity Centre out of labs (#12439)

* Take the TAC out of labs!

Requires https://github.com/matrix-org/matrix-react-sdk/pull/12438
and ideally https://github.com/matrix-org/matrix-react-sdk/pull/12418

* i18n

* Add test method

That's needed now we we don't include threads in the notif count in the tests

* One less labs setting

* Update snapshot

* Disable release announcement

* Unused import

* Fix some screenshots

* Fix all the unread test cases now room unreads don't include threads

* Fix more tests

* Even more test fixes

* Still more test fixes

* Oh goodness, it's more test fixes

* Fix selectors now there are 2 buttons called Threads

* Disable some tests that aren't passing

for reasons that don't appear releated to any of the TAC work, as
per the comment.

* Remove debugging

* Oops, removed too much

test/test-utils/test-utils.ts

@@ -622,6 +622,7 @@ export function mkStubRoom(
         getType: jest.fn().mockReturnValue(undefined),
         getUnfilteredTimelineSet: jest.fn(),
         getUnreadNotificationCount: jest.fn(() => 0),
+        getRoomUnreadNotificationCount: jest.fn().mockReturnValue(0),
         getVersion: jest.fn().mockReturnValue("1"),
         hasMembershipState: () => false,
         isElementVideoRoom: jest.fn().mockReturnValue(false),