[RTA/DPA BW tests]: Follow-ups from !405

• I think stream_config can now be a member of FileNameHelper - this would require lots of changes but would be a nice simplification,
• Line descriptors: still need to use the same streaming configuration as the rest of the test. We can load up the stream config JSON and use it to filter the lines by name to ensure this (!409 (merged)),
• hrefs can be handled better in the html maker - we can write a helper in bandwidth_helpers for this,
• Try to fix error code for make_bandwidth_test_page.py and then use it in the handler for more error checking
• The spruce stream configs should be ["full", "turbo", "turcal"] - changes required in lots of places, but this would obviate lots of mapping in the pages.
• Many different namings in KNOWN_WORKING_GROUPS and CUSTOM_WGS for track efficiency lines. Probs we just need only one.
• per-WG TotalInclusive bars in bar charts aren't lining up with the table above them
• Pages should list sample info if they can find it in the input config - see this suggestion