Use Intl to localise dates and times (#11422)

* Use Intl to generate better internationalised date formats

* Get `Yesterday` and `Today` from Intl also

* Correct capitalisation blunder

* Fix formatTime include weekday

* Iterate

* Fix tests

* use jest setSystemTime

* Discard changes to cypress/e2e/settings/general-user-settings-tab.spec.ts

* Discard changes to res/css/_components.pcss

* Discard changes to res/css/views/elements/_LanguageDropdown.pcss

* Discard changes to src/components/views/elements/LanguageDropdown.tsx

* Add docs & tests for getDaysArray & getMonthsArray

* Discard changes to test/components/structures/__snapshots__/MatrixChat-test.tsx.snap

* Consolidate consts

* Improve testing & documentation

* Update snapshot

* Apply suggestions from code review

Co-authored-by: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>

* Iterate

* Clarify comments

* Update src/DateUtils.ts

Co-authored-by: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>

* Specify hourCycle

* Discard changes to test/components/views/settings/devices/DeviceDetails-test.tsx

* Update comments

---------

Co-authored-by: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>

src/components/views/dialogs/ForwardDialog.tsx

@@ -216,6 +216,7 @@ const ForwardDialog: React.FC<IProps> = ({ matrixClient: cli, event, permalinkCr
         },
         event_id: "$9999999999999999999999999999999999999999999",
         room_id: event.getRoomId(),
+        origin_server_ts: event.getTs(),
     });
     mockEvent.sender = {
         name: profileInfo.displayname || userId,