[WEBRTC-2325] [FIX] Handle CallKit Mute / Unmute buttons

[gbattistel]

WEBRTC-2325 [FIX] Handle CallKit Mute / Unmute buttons

Features and Improvements:

Add isAudioTrackEnabled property to Peer class

• Introduces a computed property isAudioTrackEnabled in the Peer class to check if the first audio track is enabled.
• Supports both PlanB and Unified Plan SDP configurations.
• Defaults to false if no audio track is available.

Add isMuted property to Call class

• Adds a new property isMuted to determine the mute state of a call.

Handle mute/unmute actions via CXSetMutedCallAction (Demo App)

• Implements provider(_:perform:) to handle mute/unmute actions through CallKit's CXSetMutedCallAction.
• Updates the Call class by integrating muteAudio() and unmuteAudio() methods to manage audio state.
• Ensures actions are fulfilled after processing for CallKit compliance.

Synchronize mute state across components

Updates the Call mute/unmute state by:

• Accessing the call’s mute status.
• Propagating updates to CallKit by executing the corresponding mute/unmute action.

Sync mute button state in CallView on foreground entry

• Ensures the mute button in the CallView reflects the call's mute state when the app enters the foreground.