[ios-live-streaming] Unable to switch to front camera on low spec devices due to hard wired AVCaptureSession

[philcluff]

Today, we use a fixed AVCaptureSession:

.sessionPreset: AVCaptureSession.Preset.hd1920x1080,

This means that if you're trying to use an iPhone 6/6s/6+, you're unable to use the front camera, as they only have 720p front cameras.

We should pick a session preset that's limited by the worst camera on the device instead.

The table on this SO answer should be useful: https://stackoverflow.com/questions/19422322/method-to-find-devices-camera-resolution-ios