Prepare for Element Call integration (#9224)

* Improve accessibility and testability of Tooltip

Adding a role to Tooltip was motivated by React Testing Library's
reliance on accessibility-related attributes to locate elements.

* Make the ReadyWatchingStore constructor safer

The ReadyWatchingStore constructor previously had a chance to
immediately call onReady, which was dangerous because it was potentially
calling the derived class's onReady at a point when the derived class
hadn't even finished construction yet. In normal usage, I guess this
never was a problem, but it was causing some of the tests I was writing
to crash. This is solved by separating out the onReady call into a start
method.

* Rename 1:1 call components to 'LegacyCall'

to reflect the fact that they're slated for removal, and to not clash
with the new Call code.

* Refactor VideoChannelStore into Call and CallStore

Call is an abstract class that currently only has a Jitsi
implementation, but this will make it easy to later add an Element Call
implementation.

* Remove WidgetReady, ClientReady, and ForceHangupCall hacks

These are no longer used by the new Jitsi call implementation, and can
be removed.

* yarn i18n

* Delete call map entries instead of inserting nulls

* Allow multiple active calls and consolidate call listeners

* Fix a race condition when creating a video room

* Un-hardcode the media device fallback labels

* Apply misc code review fixes

* yarn i18n

* Disconnect from calls more politely on logout

* Fix some strict mode errors

* Fix another updateRoom race condition

src/settings/SettingsStore.ts

@@ -449,7 +449,12 @@ export default class SettingsStore {
      */
 
     /* eslint-enable valid-jsdoc */
-    public static async setValue(settingName: string, roomId: string, level: SettingLevel, value: any): Promise<void> {
+    public static async setValue(
+        settingName: string,
+        roomId: string | null,
+        level: SettingLevel,
+        value: any,
+    ): Promise<void> {
         // Verify that the setting is actually a setting
         const setting = SETTINGS[settingName];
         if (!setting) {