make ref work more like this

[drewbanin]

This is an object with a __repr__ that renders the model as "schema"."table". You can also access This.table, This.schema, and This.name

Ideally, ref would return a similar type of object. Then you could do:

{% set my_model = ref("my_model") %}
adapter.get_columns_in_table(my_model.schema, my_model.table)

Or, we could just pass the return value from ref through to get_columns_in_table, and the function would handle grabbing schema/table from the ref'd model.

This is going to be super important when model can be materialized in different schemas