Support crosstalk sims with real observations

[tskisner]

• Support real metadata names as seen in a typical observation.
• If using real observations, do not require DetMap.
• Refactor crosstalk utils to extract code that is common between the simulated and real observing cases.
• In SimSSO operator, apply detector cuts if they exist.
• When using real data, translate band names to expected format
• Add det_mask trait and handle detectors which are flagged as invalid.
• Update detector flags if saturated
• Add support for per-detector elevation. Remove calculation of loading based on the TOD.

[tskisner]

I will rebase this work after #1630 is merged.

[tskisner]

Ok, @tpsatt this is ready for re-review. I updated the unit test so that it is not run unless jbolo is found and the appropriate environment variables are set. For example, to run the unit test locally, ensure that DetMap and JBolo are installed and then do something like:

JBOLO_PATH="/path/to/jbolo" \
JBOLO_MODELS_PATH="/path/to/bolocalc-so-model" \
OMP_NUM_THREADS=4 \
pytest -s sotodlib/tests/test_sim_mumux_crosstalk.py

[tpsatt]

Confirming that the unit tests work, and that this produces sensible CMB sims for the LAT D56 region

[tpsatt]

Great changes