Add a playback_state prop to Audio and Video components

[freddyaboulton]

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Is your feature request related to a problem? Please describe.
Would be great to update the playback state of the audio component (current timestamp, paused/playing, etc) by returning a gr.Audio.

This could be useful in transcription demos when you want to move the audio to the timestamp a particular word was detected.

[freddyaboulton]

We should do the same for video but let's focus on audio first as users have asked for this.

[abidlabs]

How about a timestamp parameter that can be used to set the initial time position of a gr.Audio component, or to update its time position?

Related: #9126, #3965

[freddyaboulton]

Was thinking a playback_state dictionary with {"timestamp":, "paused"} and then we can add more props in the future

[abidlabs]

What other props could we potentially add?

[freddyaboulton]

Mute, volume level, playback speed