Update BandwidthTestHandler to compare with ref build
Thanks to @rmatev for implementing the PR/Moore_hlt2_bandwidth and PR/Moore_spruce_bandwidth labels, the BW tests can now be launched in any ci-test if required.
This MR allows the BandwidthTestHandler to compare test results from a lhcb-master-mr build with its reference lhcb-master build. A page showing the differences will be produced, a preview here. The increases are marked in red and decreases are marked in green.
The following message will be posted to the MR:
Bandwidth test Moore_hlt2_bandwidth: Total rate = 775.0 kHz - change of 0.00% vs. reference. Total bandwidth = 46.0 GB/s - change of 0.00% vs. reference. No new line is added, 976 lines have a rate of 0 Hz and 115 have a rate higher than 1000 Hz.
Requires lhcb-datapkg/PRConfig!317 (merged).