Remove fMP4 requirement from sink

[kixelated]

We currently use the hang::cmaf::import module. This simplifies the plugin implementation, but it requires muxing into low-latency fMP4 earlier in the pipeline only to demux it layer.

Ideally, we should properly populate the catalog and tracks based on the pads. The fMP4 pipe could be fully removed then.

[gehirndienst]

not to mention, it prevents you from streaming live media