Improve performance

[SuperQ]

Bump pro-bing to integrate upstream BPF filter improvement.

• Add automatic handling of GOMAXPROCS.
• Document GOMAXPROCS.

[SuperQ]

Here is a performance comparison with the last release:

The test is on a 13th Gen Intel(R) Core(TM) i7-1365U 12-CPU system, with the smokeping prober configured to ping 100 localhost IPs.

The top line is the smokeping prober, the lower line is the Prometheus monitoring it.

• The first section (over 1.0 CPUs) is the old release (GOMAXPROCS=12).
• The second section (0.45 CPUs) is the old release with GOMAXPROCS=2.
• The third section (0.35 CPUs) is the new pro-bing library with GOMAXPROCS=2.
• The last section (0.25 CPUs) is the new pro-bing library with GOMAXPROCS=1.