dev/ci: buildkite logs to Grafana Cloud

Created by: bobheadxi

We should build a tool to dump buildkite logs for the last N runs for various criteria to analyse certain classes of errors. This will help us prioritize our efforts, and will be faster for aggregating metrics than waiting for feedback from engineers who notice flakes.

Part of https://github.com/sourcegraph/sourcegraph/issues/25768: https://docs.google.com/document/d/1fknr3NQGmwbKCfnF3Bcr-tYzV-TeuAGq-_Tm2-z_09M/edit#heading=h.5j0qk4kldt4s