External forces space per worker adjustment integration

[akselx]

This PR is focused on:

1. updating space per worker assumptions to current (2023) levels
2. making future assumptions to space per worker levels in forecast years (focused on the period 2025-2035)

It leverages research on space per worker trends nationally and locally to create updated adjuster files. The adjuster files are already used by the model system to apply cross-sectional detail to the regional space per worker constants.

The PR updates the existing function sqft_per_job in variables.py in the following ways:

• It departs from the existing version by applying adjusters to just office buildings. The existing version applied adjusters to all buildings.
• To allow for flexibility in time specificity in passed adjusters, it checks for the existence of adjusters for a particular simulation year. If present it uses that. If not it looks for the generic, time-invariant adjuster column.
• To allow for adjusters to be optionally applied to non-office buildings - more similar to the legacy version - the function now checks for a yaml flag, and potentially adjusts with the time invariant or 2010 values, if multiple are available. This current bandaid fix means we include some cross-sectional adjuster detail, adding more subregional granularity, while not making strong assumptions about the future direction in space per workers for the non-office building stock. A future version could allow for building-type specific adjusters.

Other changes

• To test effects on office space development of reduced space per worker assumptions requires vacancy rates to drop below a certain threshold. Insofar as the development pipeline has considerable amounts of space, a runtime filtering option was added to drop pipeline projects based on criteria set in a separate yaml file. This was included in this PR.