TIMESTAMP columns should use "timestamp with time zone", not "timestamp" (without time zone)

[e-gineer]

We're currently setting TIMESTAMP columns to use timestamp:

steampipe-postgres-fdw/sql/sql.go

Line 65 in e5a1ccf

return "timestamp", nil

But, that means we are ignoring timezone information. We should instead be using timestamp with time zone.

Details - https://medium.com/building-the-system/how-to-store-dates-and-times-in-postgresql-269bda8d6403