PG17.0 Support - SQL changes, new features

[naisila]

(Issue still under construction ...)

We need to support the following, or print meaningful error messages for currently unsupported features in Citus

• PG 17 introduced a new ACL called ACL_MAINTAIN
  PG commit:
  ecb0fd33720fab91df1207e85704f382f55e1eb7
  postgres/postgres@ecb0fd3
  Our deparser does not handle that
  

  citus/src/backend/distributed/deparser/citus_ruleutils.c

  Line 1351 in f695971

  elog(ERROR, "unrecognized aclright: %d", aclright);

• MergeAction can have 3 merge kinds (now enum) in PG17, write compat
  Relevant PG commit:
  0294df2f1f842dfb0eed79007b21016f486a3c6c
  postgres/postgres@0294df2
  New merge kinds should be handled in deparser and Merge logic in Citus.
  - MATCHED BY SOURCE
  - MATCHED_BY_TARGET

• Supporting MEMORY option when extracting EXPLAIN output from workers.
  

  citus/src/backend/distributed/planner/multi_explain.c

  Line 1098 in f695971

  /* use the same defaults as NewExplainState() for following options */

  
  For now we will not be showing memory usage from workers if we do not add support for this.