Evaluate possible performance degradation pattern with growing builds

Description

We want to better understand the possible degradation pattern if ci_builds table keeps growing and we do not deliver partitioning.

Proposal

Replicate what Nikolay's team did in case of ci_pipelines partitioning, but without partitioning, and add more builds to see when the performance starts decreasing. Add builds up to the point of an synthetic environment outage and plot chart with transactions-per-second in time.

/cc @NikolayS @jreporter