Convert ddlutils regression tests to TAP tests.

Convert ddlutils regression tests to TAP tests.

The regression tests for pg_get_role_ddl(), pg_get_database_ddl(),
and pg_get_tablespace_ddl() created databases and tablespaces, which
are heavyweight operations.  As noted by Andres Freund, this is
wasteful in the core regression suite which gets run repeatedly.

Convert the three test files (role_ddl.sql, database_ddl.sql,
tablespace_ddl.sql) into a single TAP test that runs once, covering
all the same functionality: basic DDL generation, pretty-printing,
option handling, error cases, permission checks, and edge cases like
quoted names and role memberships.

Discussion: https://postgr.es/m/5c67dc79-909a-4e17-8606-6686667da6c6@dunslane.net