[xCluster] DDL replication - support array types

[mdbridge]

Jira Link: DB-12972
These are somewhat tricky as there are no specific DDL for creating
them, just creating or altering objects like tables that use them. For
example:

CREATE DOMAIN postal_code AS TEXT
             CHECK(VALUE ~ '^\d{5}$'OR VALUE ~ '^\d{5}-\d{4}$');
CREATE TABLE foo(postal postal_code[]);
INSERT INTO foo values (array['32768', '65536']::postal_code[]);
select * from foo;

Here postal_code[] is an array type with base type domain postal_code.

The hard part is that the pg_type OID of the base type must be identical
on both universes.

I believe this means that all pg_type OIDs must be preserved across the
universes as DDL's are done. (Bootstrap takes care of setting them up
as the same initially.)

We don't strictly need array pg_type OIDs preserved (the base type of an
array is never another array type), but I don't know if that is helpful.