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/components/views/settings/tabs/user/LabsUserSettingsTab-test.tsx

@@ -60,7 +60,7 @@ describe("<LabsUserSettingsTab />", () => {
         // non-beta labs section
         expect(screen.getByText("Early previews")).toBeInTheDocument();
         const labsSections = container.getElementsByClassName("mx_SettingsSubsection");
-        expect(labsSections).toHaveLength(11);
+        expect(labsSections).toHaveLength(10);
     });
 
     describe("Rust crypto setting", () => {