Support `SELECT * FROM function()` syntax

[tbantle22]

In Postgres, you can select from functions by doing either:

SELECT function();
SELECT * FROM function();

SELECT function() is supported, but we need to support SELECT * FROM function() as well.

TypeORM uses select * from current_database() and select * from current_schema(), which we implemented this workaround for. We should officially support that syntax eventually.

[jennifersp]

Added in #1077