[camera_avfoundation] handle interruptions and use single offset

[misos1]

Handle interruptions of capture sessions by doing "internal pause". Another possibility would be to remove audio input from the session but this would be too specific for interruptions caused by an incoming call or alarm. Or to stop video recording as the native ios camera app does but this would require some additional event.

Handle asynchronous error notifications posted about capture sessions. This can happen for example when there is an incoming phone call and the camera starts recording with audio. For this specific case would be enough to just call startRunning on capture sessions but that is too specific and would require ability to restart capture session from dart side as seems there is no good way how to test when such phone call or other such event ends, and trying to restart it for example every second inside FLTCam does not look like good idea. Instead the camera controller enters an error state and can be recovered by disposing and recreating which should be more generic.

Use single offset for both video and audio as separate offsets can cause unsynchronized video with audio. Seems audio timestamps tend to be ignored except for the first sample so prefer them for calculating offset to avoid desynchronization. Avoid errors when trying to append samples with timestamp less or equal to the previous sample. Fix a bug when after adjusting offset also last sample time needs to be updated to avoid adding past offsets multiple times.

• fixes [camera_avfoundation] Separate time offsets for video and audio can cause shifted audio flutter#149978
• fixes [camera]When is recording interrupted by alarm or phone call video is not synchronized with audio flutter#151253

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[misos1]

Mac_arm64 ios_platform_tests_shard_2 master
Testing failed:
	Type 'AVCaptureSession' has no member 'wasInterruptedNotification'
	Command SwiftCompile failed with a nonzero exit code
	Testing cancelled because the build failed.

I am not sure what this should mean. AVCaptureSession.wasInterruptedNotification should be there since ios 4 (I managed to run tests successfully locally on real device and also on simulator).