supernova: plugin interface - use system memory allocator for nrt synthesis

when doing nrt synthesis, we do not need to use the rt memory allocator

Signed-off-by: Tim Blechmann <tim@klingt.org>
server plugins: RecordBuf - fix multichannel corruption and buffer overrun

Signed-off-by: Tim Blechmann <tim@klingt.org>
supernova: sndfile backend - use std::atomic

Signed-off-by: Tim Blechmann <tim@klingt.org>
supernova: sndfile backend - set thread names

Signed-off-by: Tim Blechmann <tim@klingt.org>
supernova: sndfile backend - ensure correct output of full frames

Signed-off-by: Tim Blechmann <tim@klingt.org>