CI: Signal significant changes in throughput w.r.t. master

Signal significant changes in throughput w.r.t. master

1. Define the thresholds (+-0.5% are used for Moore's tests).
2. Fail throughput jobs where there is a significant decrease in throughput, and possibly label with hlt1-throughput-decreased
3. Do nothing when there is an increase or add a label like hlt1-throughput-increased

Triggered by !473 (comment 4292984)

There has to be a failing (red) job or a message such as for HLT 2 throughput tests. Clicking through job logs is too time consuming.

For a broader overhaul of the CI see #235 (closed)