Change quantizer range for Av1 from 0-63 to 0-255

[Djuffin]

The AV1 spec use quantizer range 0-255. (It's called QIndex there, hence the confusion)
libaom exposes quantizer range 0-63.

We don't want to lock in on a single implementation and need to adhere to the spec.
We'll need to change the av1 entry in the webcodecs registry.

Safari and FireFox don't support quantizer bitrate mode yet.

The implementation in Chromium will need to be fixed.