mpi/pmix: Add preproc macro to remove pmix list debug overhead

Ping-pong latency effect:
size    UCXv7   UCXv8
1       18.8    17.7
2       18.7    17.7
4       18.7    17.9
8       19.2    18.3
16      19.3    18.4
32      19.4    18.3
64      19.5    19.0
128     20.2    19.4
256     20.4    19.8
512     20.6    19.9
1024    20.5    19.7
2048    21.6    20.9
4096    24.6    23.7
8192    27.7    27.2
16384   30.7    30.3
32768   36.1    35.5
65536   47.8    47.4
131072  72.2    71.4
262144  2229.3  2197.0
524288  2817.8  2727.1
1048576 3693.1  3580.4
2097152 6148.5  6120.7
4194304 10230.7 10329.2

Signed-off-by: Artem Polyakov <artpol84@gmail.com>