test: track usage of hard-coded scaler clock frequencies

[c-dilks]

The DSC2 and STRUCK scaler clock frequencies are stored in CCDB, but they are also hard-coded. This branch adds a magic number to each of the hard-coded assignments, and checks for that magic number when they're (likely) used. Printouts to stderr starting with clockbug are used to investigate.

[baltzell]

What's the measured value of the hardware clock in question? This isn't affected by both DCS2 and Struck scalers.

[c-dilks]

I'm more concerned about ambiguity in the code as to whether a CCDB value is used or a hard-coded value is used here. Even if the real clock frequency never changed, we should either use a CCDB value everywhere, or define the hard-coded frequency in one single place only; the current software both uses a CCDB value and uses hard-coded values defined in 3 places, and the value is mutable.

Here are the frequencies:

• DSC2
  • according to CCDB:
    • 1 MHz before run 14776 (from 2021 HPS run)
    • 100 kHz afterward
  • clock vs. timestamp indicates RG-A Spring 2018 may have used ~100 MHz
• STRUCK
  • always 1 MHz according to CCDB

If the hard-coded 1 MHz is used for DSC2 for runs after 14776 to estimate the charge, that's a problem.

This PR's branch should be tested on all the usual call graphs, including:

• recon-util / run-clara
• postprocess
• running with recharge true vs. false (rebuild-scalers)

[baltzell]

Note the DSC2 and Struck are different hardware, and can have different clocks.