Improve townhome fuzzy grouping, conditionally add 211s to townhome groups

[dfsnow]

In 2022, we improved the townhome valuation methodology by implementing "fuzzy grouping". Basically, townhome units with similar, but not perfectly identical, features should receive similar values.

Valuations pointed out that 211s are often mixed into townhome (210) complexes, such that you may have an alternating 211 - 210 - 211 - 210 pattern. Due to the different methodologies between 210s and 211s, neighboring units may receive very different values.

We should expand the fuzzy grouping methodology to include 211s for 211s mixed in with townhome classes. We can use the building touching indicator (ccao-data/data-architecture#7) to help identify such 211s.

[dfsnow]

I'm bumping this from this year's modeling efforts since it's likely high effort but low impact, particularly compared to other issues we can take this year.