Support sample_weight in buildstock.csv

[joseph-robertson]

Pull Request Description

Adds support for a sample_weight column in the precomputed buildstock.csv. By default, BuildExistingModel writes build_existing_model.sample_weight based on calculating n_buildings_represented / n_datapoints (this calculation is done in the workflow generator and then passed into the BuildExistingModel measure). Now, if sample_weight already exists in the buildstock.csv, it will write this value instead of the calculated one.

This PR also:

• removes registering of weight - it doesn't appear to be used anywhere
• removes the number_of_buildings_represented argument from BuildExistingModel - it appears it was only being used in the context of a PAT project, which we no longer support

Checklist

Not all may apply:

• [x] Tests (and test files) have been updated
• [ ] ~Documentation has been updated~
• [x] Changelog has been updated
• [x] openstudio tasks.rb update_measures has been run
• [x] No unexpected regression test changes on CI (checked comparison artifacts)

[joseph-robertson]

Should the new allowable column, for consistency, be "Sample Weight" instead of "sample_weight"?