WebRTC is now at M75

After calling startService we are supposed to have a bit of time before turning
the service into a foreground service, but certain devices seem to be more
spartan and we've seen the following failure:

Caused by java.lang.IllegalStateException: Not allowed to start service Intent { act=JitsiMeetOngoingConferenceService:START cmp=org.jitsi.meet/.sdk.JitsiMeetOngoingConferenceService }: app is in background uid UidRecord{f6778d5 u0a220 CAC  bg:+1m1s417ms idle change:idle procs:1 proclist:15604, seq(0,0,0)}
       at android.app.ContextImpl.startServiceCommon + 1600(ContextImpl.java:1600)
       at android.app.ContextImpl.startService + 1546(ContextImpl.java:1546)
       at android.content.ContextWrapper.startService + 669(ContextWrapper.java:669)
       at org.jitsi.meet.sdk.JitsiMeetOngoingConferenceService.launch + 50(JitsiMeetOngoingConferenceService.java:50)

Be expliocit and call startForegroundService, on supported platforms.

Brings back the button for generating meeting URLs for calendar events.

I cannot see a path leading to it being null, but Crashlytics demonstrated it's
possible (so far in a small subset of old devices). Be defensive then.

The app is about to crash at that stage so it was a moot point to try to leave
the conference anyway.

Stopping ConnectionServers is still a good idea though, since a crash may leave
the device in a bad state otherwise.

Fixes this issue:

~~~
    java.util.ConcurrentModificationException
        at java.util.HashMap$HashIterator.nextNode(HashMap.java:1441)
        at java.util.HashMap$KeyIterator.next(HashMap.java:1465)
        at org.jitsi.meet.sdk.OngoingConferenceTracker.updateListeners(OngoingConferenceTracker.java:89)
        at org.jitsi.meet.sdk.OngoingConferenceTracker.onExternalAPIEvent(OngoingConferenceTracker.java:74)
        at org.jitsi.meet.sdk.ExternalAPIModule.sendEvent(ExternalAPIModule.java:71)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.facebook.react.bridge.JavaMethodWrapper.invoke(JavaMethodWrapper.java:372)
        at com.facebook.react.bridge.JavaModuleWrapper.invoke(JavaModuleWrapper.java:158)
        at com.facebook.react.bridge.queue.NativeRunnable.run(Native Method)
        at android.os.Handler.handleCallback(Handler.java:873)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at com.facebook.react.bridge.queue.MessageQueueThreadHandler.dispatchMessage(MessageQueueThreadHandler.java:29)
        at android.os.Looper.loop(Looper.java:214)
        at com.facebook.react.bridge.queue.MessageQueueThreadImpl$4.run(MessageQueueThreadImpl.java:232)
        at java.lang.Thread.run(Thread.java:764)
~~~

It causes a compiler error in Xcode 11 because it doesn't know how to parse it.

this._room should be used only by jitsi-meet-torture and for test purposes. Also this._room is assigned later than room. This may cause some issues, for example conference.getMyUserId() may return undefined while the user id is already available beacuse this._room hasn't been assigned yet.

* Adds a notification when remote lock happens.

* Updates translations.

Removes unused strings and extracts room password to separate translation, to be able to change it when deployment uses only digits.

* Formats the conference pin when showing it.

* Removes member from translation in favour of participant.

* Updates formatting of the pin.

* Adds a notification when password is remotely removed.

* Adds back talk while muted notification.

* Adds unmute button to the notification.

* Adds option to be able to cancel locked rooms and leave.

* Removes not needed operations when canceling password prompt.

Update LJM to 9bcc2a26cc in order to bring
in the analytics update which will add a property indicating how much
time has passed since the last successful XMPP request came through.

Join notifications are already supressed for the local
participant, so hide the left notification. For now
the notification is not being shown on mobile to keep
the same existing behavior and because a copy change
will be needed, but will be added once batching is
implemented.

* Device selection now always shows the device that managed to open.

* Simplifies implementation, skips using state.

Updates LJM to c0af82a215

The only way to render the welcome page in reduced UI mode currently is to
hangup a call from the Android ongoing notification while in PiP mode.