Feature/drop relation/ct 2581

[mikealfare]

resolves #7625

Description

Allow for a more configurable drop_relation() macro; preserve backwards compatibility.

• create adapters/drop_relation.sql
• update drop_relation() to condition on relation.type and dispatch to the appropriate macro
• create drop_table(), drop_view(), and drop_materialized_view()

Checklist

• I have read the contributing guide and understand what's expected of me
• I have signed the CLA
• I have run this code in development and it appears to resolve the stated issue
• This PR includes tests, or tests are not required/relevant for this PR
• I have opened an issue to add/update docs, or docs changes are not required/relevant for this PR
• I have run changie new to create a changelog entry

[mikealfare]

I moved all of the drop_relation() macros into their own file because now there's several macros that are all related to each other. However, I could also see an argument for keeping drop_relation() and default__drop_relation() in adapters/relation.sql to act as an interface, and then putting macros like drop_view() in a file adapter/view.sql along with similar implementations of other macros (e.g. create_view(), rename_view(), etc.). In the latter pattern, we'd also have adapters/table.sql and adapters/materialized_view.sql files.

[aranke]

LGTM!