Generate a native ORCA plan for a replicated CTE in scalar subqueries

[Alena0704]

When a CTE over a DISTRIBUTED REPLICATED table is referenced from several
scalar subqueries, ORCA puts the SharedScan Producer and Consumer on
different slices. That cross-slice SharedScan used to hang.

Until now we just avoided the hang: FHasCrossSliceReplicatedCTEConsumer
detected this shape before DXL translation and fell back to the Postgres
planner. This change lets ORCA handle the scalar-subquery case natively,
so no fallback is needed: the replicated CTE is materialized once and
shared by all references inside ORCA's own plan.

The fix is in apply_shareinput_xslice (src/backend/cdb/cdbmutate.c). When
a cross-slice Consumer is found inside a SubPlan and the CTE source is a
replicated table, the Consumer gets its own local copy of the Producer's
subtree (Materialize + base Scan) with a fresh share_id, marked
SHARE_MATERIAL and placed in the Consumer's slice. The table is
replicated, so every segment already has the full data and the local copy
is equivalent -- this removes the cross-slice coordination. Other
Consumers of the same CTE in the same slice reuse this copy (tracked by
(orig_share_id, motId) -> new_share_id), so the CTE is materialized once
and read by all references. cleanup_orphaned_producers then drops the
original Producers that are no longer used. The reuse map and consumer
counts live in new ApplyShareInputContext fields in
src/include/nodes/relation.h.

The pre-DXL fallback check (CUtils::FHasCrossSliceReplicatedCTEConsumer)
was too broad -- it fired for every cross-slice replicated CTE Consumer.
Narrow it to the join case only: a CTE Consumer under a
duplicate-hazard / broadcast Motion (greengage 51fe92e), which still
can't be handled natively. The scalar-subquery case no longer matches
here and reaches the new materialization path instead.

[Alena0704]

I decided to create about new pull request because we fixed that problem before with fall back walker and now I am developing approach making orca builds the query plan for cross slice scalar subqueries without breaking the semantics of checking cross slice pattern for other components with replicated tables (the regression test proved it).

FYI, the previous PR to fix this topic and discussion #370