Generate periodic flame graphs for Gitaly

In a recent conversation the @pks-t and @samihiltunen, they mentioned that they don't have the means to perform profiling on the Production Gitaly servers. When we (Scalability) generate flame graphs, we do this with production access and they are understandably hesitant to have the same access.

We could build a mechanism that runs on each server to periodically generate flame graphs and deliver them to a central location where they can be accessed. At a later stage, we could change the frequency or introduce an "on-demand" mechanism. For a first iteration, periodic graphs should meet this need.

Status 2022-04-05

Production rollout is complete!

See here for a results summary and reference for how to access and use this data: #1433 (comment 901717231)