Enable WRITE_READ_PARSE_PLAN_TREES of rewritten utility statements
This was previously disabled because we lacked outfuncs/readfuncs
support for most utility statement types.
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://www.postgresql.org/message-id/flat/
4159834.
1657405226@sss.pgh.pa.us