Less stringent run_analysis.rb dependencies

[joseph-robertson]

Pull Request Description

Avoid loading openstudio at the top of buildstock.rb. For example, we don't need it when only running sampling using run_analysis.rb.

Checklist

Not all may apply:

• [ ] ~Tests (and test files) have been updated~
• [ ] ~Documentation has been updated~
  • [ ] ~If related to resstock-estimation, checklist includes data dictionary, source report, options_lookup.~
  • [ ] ~If changes to project_testing tsvs, checklist includes yml_precomputed, yml_precomputed_outdated, yml_precomputed_weight~
• [ ] ~Changelog has been updated~
• [x] openstudio tasks.rb update_measures has been run
• [x] No unexpected regression test changes on CI (checked comparison artifacts)