fix: use separate AudioContexts for each media element?

[WofWca]

Using a shared one causes problems. See

jumpcutter/src/entry-points/content/StretchingController/StretchingController.ts

Lines 227 to 232 in 1c82c22

	// This is mainly to reduce CPU consumption while the video is paused. Also gets rid of slight misbehaviors like
	// speed always becoming silenceSpeed when media element gets paused, which causes a guaranteed audio stretch on
	// resume.
	// TODO This causes a bug - start playing two media elements (on the same <iframe>), then pause one - both will get
	// silenced. Nobody really does that, but still.
	const suspendAudioContext = () => audioContext.suspend();

Maybe there are other problems related to this.
It should also prepare us for potentially attaching to several elements on the same document simultaneously.

IIRC the only benefit of using a shared one is performance. Not sure how bad creating several AudioContexts is, but I'm sure not super bad. But currently we only use one Controller at a time anyway, so it's not that we're gonna have a bunch of AudioContexts at simultaneously.
It used to be the case before fa678bf.

So I think we need to create a new one on each controller initialization.