Support PostGIS and Enum data types

[iskakaushik]

Enums

PG -> PG

• If enum exists and cardinality matches - use the enum type
• Else store as VARCHAR

PG -> SF/BQ

• Store as VARCHAR

Geospatial

• PG -> PG the datatypes should be matched perfectly.
• PG -> SF - https://docs.snowflake.com/en/sql-reference/data-types-geospatial#label-data-types-geography where possible and VARCHAR otherwise.
• PG -> BQ - https://cloud.google.com/bigquery/docs/reference/standard-sql/data-types#geography_type where possible and VARCHAR otherwise

[iskakaushik]

also support HSTORE

[iskakaushik]

@Amogh-Bharadwaj can you split this issue into 3 parts:

1. Enum
2. PostGIS
3. HSTORE

and close the ones that are actually complete.

[Amogh-Bharadwaj]

Split this issue into 4 and marked 1 as completed

[serprex]

Issues: #563 #564 #565 #566

[Amogh-Bharadwaj]

Geospatial support for BigQuery:
#963

Geospatial support for Snowflake:
#516

HStore and Geospatial support for PostgreSQL:
#1091

Enum tests:
#1025

HStore for Snowflake:
#1047

HStore for BigQuery:
#995