[RTA/DPA BW tests]: Minor follow-ups from !374 and !393

FYI @lugrazet

• this discussion - hopefully remove a slightly-hidden copy,
• this discussion - reduce boilerplate/code duplication in html
  • Much cleaner html handling now from !384 (merged)
• this - just make the html files you need, not copy them?
• this - over-specification
  • Much cleaner html handling now from !384 (merged)
• this discussion - misleading multiple-processes argument.
• Trim down text in the bandwidth pages if we can
  • Much cleaner html handling now from !384 (merged)
  • Always more to be done on this front so I won't tick the box 😉

Some makeover related comments are being addressed !384 (merged)

More from !393 (merged)

• csv files for download for all_lines_per_production_stream and the all_lines_per_production_stream_per_wg? No, the per-WG pages have titles/headers etc. All the same info is there in principle in the all-lines-csv.
• Rate/bandwidth tables for each stream, split also by WG, with 1 row per trigger line and Rate/bandwidth tables for each stream, with 1 row per trigger line are essentially duplicated for the sprucing test
• Consistent function naming scheme in combine_rate_output.py
• Can we dynamically grab the stream assignment regexs from sprucing production files in Moore? Rather than having to duplicate them and stay aligned.

Wish list

• Do the comparison by line by bandwidth (rather than/in addition to rate),
• Comparison should catch cases where the line was removed, not only added,
• Extra words on comparison page to tell people how to read it, particularly if there are multiple MRs contributing/reference hasn't been updated since last merge : lhcb-core/LHCbPR2HD!299 (merged)
• We don't currently see per line changes due to persistence, as the rate doesn't change. Would be alleviated by comparing as function of bandwidth.
• Checking success based on more than just error codes - #16 (closed) shows us that sometimes the software can fail but also terminate successfully and give a 0 error code. It'd be good to catch this.
• Comparison page shouldn't report NaNs - instead do N/A or "-"
• The automated Gitlab comments should say whether any line rates changed or not - this would indicate to people whether they should bother checking the comparison page.