Re: Pass ParseState as down to utility functions.

hi.

ATExecAddOf
DefineType
ATPrepAlterColumnType
ATExecAlterColumnType
DefineDomain
AlterType
i changed the above function, so the above related function errors may
print out error position.
reason for change mainly because these functions have
`typenameType(NULL, typeName, &targettypmod);`
we want to pass not NULL pstate (typenameType(pstate, typeName, &targettypmod);)

why do we want printout error position
1. it can quickly locate DDL command error positions, beginner friendly.
2. in the thread `CREATE SCHEMA ... CREATE DOMAIN support`, case like:
CREATE SCHEMA regress_schema_2
create domain ss1 as ss
create domain ss as text;
ERROR: type "ss" does not exist
obviously the error is not helpful at all.

As you can see, in cases like a single DDL, multiple sub DDL within
it, error position is quite important
I also added some tests for DefineDomain.
added parser_errposition for many places in DefineDomain.

the attached patch (based on Kirill Reshke 's v2 patch)
either passing the source_string to the existing ParseState
or by making a new ParseState passing source_string to it.
then add
`parser_errposition(pstate, location)))`
in various places optionally.

So I guess bundling it into a single patch should be fine?