get_SDA_property: CTEs for SQLite compatibility and query readability

[brownag]

This PR replaces SELECT ... INTO ... SQL syntax with Common Table Expressions (CTEs) in get_SDA_property(). Temporary tables are used in the dominant component (numeric) and weighted average aggregation methods.

• implement CTEs for Weighted Average aggregation (includes dominant component, numeric)
• implement CTEs for MIN/MAX aggregation
• Benchmark against gNATSGO and SSURGOPortal output for a few other properties (e.g. available water capacity)

This change has the benefit of increasing the compatibility of get_SDA_property() methods with SQLite and other dialects. I've done some benchmarking of old vs. new as well as against SSURGOPortal output. We have 1:1 parity across tools and dialects, and all existing soilDB tests are passing with the new code.

In this PR I've also built out the infrastructure that will make it relatively easy implement this approach for the other areas I identified in #250.

Before merging I will be testing this across the country to verify there aren't edge cases when querying multiple properties with very different patterns of missing values, and adding additional tests if needed to make sure that type of edge-case functionality is fully tested.