In WebRTC M92 the RTCAudioSession lock changed from a recursive one to a regular
mutex one, so make sure we don't attempt to lock it  while already holding the
lock.

These provide the ability to integrate the SDK with some other application
loggers.

At the time this was written we use Timber on Android and CocoaLumberjack on iOS.

In addition to the integration capabilities, a LogBridge React Native module
provides log transports for JavaScript code, thus centralizing all logs on the
native loggers.

This commit refactors device selection (more heavily on iOS) to make it
consistent across platforms.

Due to its complexity I couldn't break out each step into separate commits,
apologies to the reviewer.

Changes made to device handling:

- speaker is always the default, regardless of the mode
- "Phone" shows as a selectable option, even in video call mode
- "Phone" is not displayed when wired headphones are present
- Shared device picker between iOS and Android
- Runtime device updates while the picker is open

RTCAudioSession is a thin wrapper around AVAudioSession provided by the WebRTC
framework. It makes some use-cases easier, and leads us closer to manual audio
unit management, which we will likely need in the near future.

When we are in the default state (ie, not in a meeting) we shouldn't override
the AVAudioSession category and mode. It's a singleton and we might be bothering
other components of the host app which use it.

There is no reason for them to run on the main thread, it's safe to call
AVFoundation functions on threads other than the main thread.

The previous code made an incorrect claim about the thread in which the audio
route change notification selector is called: it's called on a secondary thread:
https://developer.apple.com/documentation/avfoundation/avaudiosessionroutechangenotification

Fixes the following warning:

~~~
Module XXX requires main queue setup since it overrides `constantsToExport` but doesn't implement `requiresMainQueueSetup`. In a future release React Native will default to initializing all native modules on a background thread unless explicitly opted-out of.
~~~

For AppInfo and AuioMode, there is no need to initialize anything in the UI
thread, so just return NO.

1. Aligns the project structure of Jitsi Meet SDK for iOS with that for
   Android for better comprehension.

2. The command `react-native run-ios` uses the last Xcode project or
   workspace in the list of these sorted in alphabetical order. Which
   limits our freedom in naming. Thus having only an Xcode project in
   the root directory of the iOS project structure gives us back the
   freedom in naming.

3. Allows the Podspec to work for the app project in addition to the sdk
   project because we need Crashlytics in the app which is integrated
   via Cocoapods as well.

4. Further removes references to JitsiKit in the source code for the
   sake of consistent naming.

Ladies and gentlemen, allow me to introduce you to Jitsi Meet SDK for iOS, the
mobile SDK which powers Jitsi Meet.

The goal is to encapsulate the entire React Native app into a framework / SDK
and offer an API for native (ObjC or Swift) applications to embed the Jitsi
conferencing experience.

While React Native can be embedded in native applications, I don't think it was
designed to be embedded as part of a framework, hidden away from the application
using it. This surfaced as a number of issues which had to be addressed
specifically due to our use-case:

- Universal / deep linking needed to be wrapped to avoid the embedding app from
  linking with RN.
- The bundle URL had to be manually constructed, since RN considers that all
  resources are in the main bundle, but in case of a framework that is not the
  case.
- Custom fonts had to be manually loaded, since UIAppFonts doesn't work on the
  framework's Info.plist file.
- The RN packager has to be manually triggered since the React project will no
  longer do it for us.
- Custom App Transport Security rules were added since the builtin way to do it
  modifies the framework's Info.plist, which is useless in this case.

At this stage, the Jitsi Meet application is just a small single view
application which uses the Jitsi Meet SDK to create a single view which
represents the entire application. Events and external conference handling are
forthcoming.

Simplify the source code (with the idea that source code which does not
exist does not have to be maintained).

Additionally, apply modifications to have the source code comply with the coding
style.

Overall, prepare saghul:audio-mode for merge into jitsi:master.