swiss: report performance counters in benchmarks

[aclements]

This adds a dependency on github.com/aclements/go-perfevent

[cockroach-teamcity]

This change is 

[aclements]

Do you know differently?

Unfortunately, that's generally true. Hardware performance counters are quite difficult to virtualize safely. I believe AWS does support hardware PMUs on some instance types, but I haven't tried it: https://www.intel.com/content/www/us/en/developer/articles/technical/intel-vtune-amplifier-functionality-on-aws-instances.html

[petermattis]

Thanks for the contribution.