Support arrays of composite types, including the rowtypes of regular tables

Support arrays of composite types, including the rowtypes of regular tables
and views (but not system catalogs, nor sequences or toast tables).  Get rid
of the hardwired convention that a type's array type is named exactly "_type",
instead using a new column pg_type.typarray to provide the linkage.  (It still
will be named "_type", though, except in odd corner cases such as
maximum-length type names.)

Along the way, make tracking of owner and schema dependencies for types more
uniform: a type directly created by the user has these dependencies, while a
table rowtype or auto-generated array type does not have them, but depends on
its parent object instead.

David Fetter, Andrew Dunstan, Tom Lane