utils: probes_demux: auto-close idle audio files and avoid overwrites

utils: probes_demux: auto-close idle audio files and avoid overwrites

Audio capture files (buffer_<id>.wav) are now automatically closed
after 200 ms of inactivity, so completed recordings can be accessed
while sofprobeclient is still running.

If the same probe point becomes active again, a new file is created
with an incrementing index (buffer_<id>-1.wav, buffer_<id>-2.wav, ...)
rather than overwriting the previous capture.  The index is chosen by
probing the filesystem, so existing files from earlier runs are never
clobbered either.

Buffer IDs in file names and log messages are printed in hexadecimal
(e.g. buffer_0x1a.wav) to match firmware conventions.

Closes: https://github.com/alsa-project/tinycompress/pull/35
Signed-off-by: Jyri Sarha <jyri.sarha@linux.intel.com>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>