uart: Add binaryout/dump support, drop obsolete 'uart_dump' PD.

uart: Add binaryout/dump support, drop obsolete 'uart_dump' PD.

The functionality of the preliminary 'uart_dump' PD is now available
in the proper 'uart' PD, via the OUTPUT_BINARY mechanism that frontends
can use to dump decoded data (in various formats) to a file, or pipe it
into other applications, and so on.

Old sigrok-cli example usage:

 $ sigrok-cli -i foo.sr -P uart:rx=0:tx=1,uart_dump:filename=bootlog.txt

New sigrok-cli example usage:

 $ sigrok-cli -i foo.sr -P uart:rx=0:tx=1 -B uart=rxtx > bootlog.txt

New sigrok-cli example usage (piping into other applications):

 $ sigrok-cli -i foo.sr -P uart:rx=0:tx=1 -B uart=rxtx | grep "whatever"