obvervability for cloud_bench

[stepashka]

add metrics to track what cloud_bench does, and what the config of the run was

• implement metrics in cloudbench https://github.com/neondatabase/cloud/pull/1257
• configure scraping in stress testing env
• add these metrics to the captest grafana dashboard so that you see the scenario that was run along with the results

metrics ideas:

• count of projects attempted to create (tasks?)
• error count of tasks (with commands as labels)
• histogram task duration for finished tasks(pgbench with commands as labels)
• run label: user+time?
• profile label
• maybe gauge/count of tasks that need to be scheduled?
• anything else?

[chaporgin]

added metrics to cap test dashboad

[chaporgin]

run label: user+time?

added user. putting time into a label will give us big cardinality, IUUC. Should we really do that?