Sizing control option to specify max allowed airflow

[jonwinkler]

@joseph-robertson @yzhou601 @shorowit

It would be useful to implement an argument for passing in the calculated maximum airflow rate for existing ducts (hvac_distribution_duct_max_airflow_cfm). Analogous to system capacities, ResStock could use ApplyUpgrade to assign the values corresponding to the existing building. This could make sizing heat pump upgrades (i.e., a new advanced HVAC sizing control input) more realistic where the maximum allowed airflow rate could be based on the baseline.

[joseph-robertson]

#1547 aims to address this. NREL/resstock#1163 tries it out in ResStock.