Remove unnecessairly duplicated gram.y productions

Remove unnecessairly duplicated gram.y productions

Declarative partitioning duplicated the TypedTableElement productions,
evidently to remove the need to specify WITH OPTIONS when creating
partitions.  Instead, simply make WITH OPTIONS optional in the
TypedTableElement production and remove all of the duplicate
PartitionElement-related productions.  This change simplifies the
syntax and makes WITH OPTIONS optional when adding defaults, constraints
or storage parameters to columns when creating either typed tables or
partitions.

Also update pg_dump to no longer include WITH OPTIONS, since it's not
necessary, and update the documentation to reflect that WITH OPTIONS is
now optional.