`howl`: add "fast" mode

[rerpha]

I haven't profiled this, but i think the main bottleneck in howl at the moment is likely going to be generating the random numbers in each event message

I would like a "fast" mode which just sends the same ev44 blobs per frame much like 9428417 does.

this should be configurable via a command line argument.

[rerpha]

@jackbdoughty you could have a go at this if you fancy doing a bit of rust