[Pg] Add implementation of geography type for PostGIS extension

[robinsimonklein]

For now, as mentioned here, Drizzle ORM only has basic support for the PostGIS extension, with only the geometry column type available. PostGIS also offers a geography column type, which is often more suitable for storing real-world location coordinates because it uses the Earth's spherical representation for calculations.

This is a first attempt to implement the geography type, based on the current implementation of geometry. Both types work similarly, with the following differences:

• The srid parameter has been removed, as the geography type only works with SRID 4326.
• xy mode has been renamed to json, and x and y have been replaced with lon and lat, which makes more sense for geographic coordinates.