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

.eslintrc.js

@@ -117,6 +117,10 @@ module.exports = {
                 "@typescript-eslint/ban-ts-comment": "off",
                 // We're okay with assertion errors when we ask for them
                 "@typescript-eslint/no-non-null-assertion": "off",
+
+                // The non-TypeScript rule produces false positives
+                "func-call-spacing": "off",
+                "@typescript-eslint/func-call-spacing": ["error"],
             },
         },
         // temporary override for offending icon require files