Feature/Databricks support

[sleblanc23]

Description & motivation

This PR, along with these changes in edu_wh, makes EDU compatible with Databricks.

TO DO: consider merging in this PR

Breaking changes introduced by this PR:

None

New files:

• Added several macros that handle differences in function syntax and complications that arise from how Databricks returns values from array functions (always as a named_struct, not a variant).
• The star macro (name suggestions welcome) implements Snowflake's exclude (which is called except in Databricks) and rename (which is not present in Databricks).

Changes to existing files:

• Cleaned up in the extract_extension macro
• Modified to the source_edfi3 and flatten_arrays macros to call new array handling macros
• Substituted a macro call in place of Snowflake-specific array behavior throughout the stage models
• Rewrote of stg_ef3__contacts and stg_ef3__student_contact_associations (pending decision on PR linked above)

Tests and QC done:

Ran in GSN and SC; confirmed that all affected models are unchanged by comparing row counts and relevant column values