In psql \d+, display oids only when they exist, and display replication
identity only when it is non-default. Also document the defaults for
replication identity for system and non-system tables. Update
regression output.
Display "replica identity" only for \d plus mode, exclude system schema
objects, and display all possible values, not just non-default,
non-index ones.
The only reason this didn't work before was that parserOpenTable()
rejects composite types. So use relation_openrv() directly and
manually do the errposition() setup that parserOpenTable() does.
The original implementation of this interpreted it as a kind of
"inheritance" facility and named all the internal structures
accordingly. This turned out to be very confusing, because it has
nothing to do with the INHERITS feature. So rename all the internal
parser infrastructure, update the comments, adjust the error messages,
and split up the regression tests.