Correct update of time in stream record - fixes failure to obtain a rate for stream using rate helper

Tidy

No, we should be reporting the rate as stored - it was calculated using a block stream rate helper and so should be right

Fix tests

Update following matrix api change

Add stateful version of channel selecting stream

For our practical purposes it seems better to treat this as reducing the rate (random access adapters for example like it better) - I hope it doesn't break anything else

Fix failure when source stream ends on block boundary

Comments and debug output only

Add an explicit mechanism to call finish (if we aren't reading to the end)

Provide a friendlier representation with times converted

Correct comment

Cepstral stream only needs magnitude as input, so make that explicit

Fix test

Correct summariser rate by using a blockstream rate helper

Add blocksize alteration to maps

Fix derivative which wasn't working correctly; add silence threshold

Comment

This seems conceptually simpler (I happened to be writing this elsewhere so thought I'd make it match)

Introduce PullResampler to make the callback-driven resample logic available to code other than direct users of ResamplingStatefulStreamFn