Make TupleDescInitBuiltinEntry throw error for unsupported types.
Make TupleDescInitBuiltinEntry throw error for unsupported types.

Previously, it would just pass back a partially-uninitialized tupdesc,
which doesn't seem like a safe or useful behavior.

Backpatch to v10 where this code came in.

Discussion: 351e117c944891793e5fa5fe48c921414bb170e3@sss.pgh.pa.us

lisakowen/gpdb,50wu/gpdb,lisakowen/gpdb,adam8157/gpdb,lisakowen/gpdb,50wu/gpdb,adam8157/gpdb,adam8157/gpdb,lisakowen/gpdb,xinzweb/gpdb,lisakowen/gpdb,xinzweb/gpdb,lisakowen/gpdb,greenplum-db/gpdb,adam8157/gpdb,greenplum-db/gpdb,greenplum-db/gpdb,50wu/gpdb,adam8157/gpdb,greenplum-db/gpdb,xinzweb/gpdb,xinzweb/gpdb,xinzweb/gpdb,50wu/gpdb,50wu/gpdb,greenplum-db/gpdb,greenplum-db/gpdb,lisakowen/gpdb,50wu/gpdb,xinzweb/gpdb,adam8157/gpdb,greenplum-db/gpdb,adam8157/gpdb,lisakowen/gpdb,xinzweb/gpdb,greenplum-db/gpdb,50wu/gpdb,adam8157/gpdb,xinzweb/gpdb,50wu/gpdb