Implement lazy AVAudioSession activation

[alexlapa]

Synopsis

A different approach to fixing #267.

Solution

If there is at least one local audio track or PeerConnection then call setCategory(playAndRecord) and setActive(true), otherwise - setActive(false).

Checklist

• Created PR:
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[alexlapa]

FCM:

Implement lazy `AVAudioSession` activation on iOS (#268)