refactor AlterDomainAddConstraint (alter domain add constraint)

hi.
attached patch refactor AlterDomainAddConstraint

* change the error message:
alter domain d_int add constraint nn not null no inherit;
from
ERROR: NOT NULL constraints cannot be marked NO INHERIT
to
ERROR: DOMAIN with NOT NULL constraints cannot be marked NO INHERIT

basically processCASbits
from
processCASbits($3, @3, "NOT NULL")
processCASbits($5, @5, "CHECK")
to
processCASbits($3, @3, "DOMAIN with NOT NULL")
processCASbits($5, @5, "DOMAIN with CHECK")

* error out check constraint no inherit with domain. so the following
should fail.
alter domain d_int add constraint cc check(value > 1) no inherit; --should fail

* delete code in AlterDomainAddConstraint, since it will be unreachable.

* alter domain d_int add constraint cc2 check(value > 11) not
deferrable initially immediate not valid;
"not deferrable", "initially immediate" cannot error out at the moment.
maybe we can just document it in create_domain.sgml?

* some failed regress test, similar to thread (Pass ParseState as down
to utility functions)

you may also see the patch draft commit message.