* change zenith-perf-data checkout ref to be main
* set cluster id through secrets so there is no code changes required
when we wipe out clusters on staging
* display full pgbench output on error
tests are based on self-hosted runner which is physically close
to our staging deployment in aws, currently tests consist of
various configurations of pgbenchi runs.
Also these changes rework benchmark fixture by removing globals and
allowing to collect reports with desired metrics and dump them to json
for further analysis. This is also applicable to usual performance tests
which use local zenith binaries.
