refactor(physical-plan): simplify `ExecutionPlan` children-replacement API

[zhuqi-lucas]

Follow-up to #23332

Per @alamb's review, landing PR #23332 leaves the ExecutionPlan trait with two methods that each build a new plan from new children:

• fn with_new_children(self: Arc<Self>, children) -> Result<...> — always recomputes PlanProperties.
• fn with_new_children_and_same_properties(self: Arc<Self>, children) -> Result<...> — reuses PlanProperties; default falls back to with_new_children.

For someone implementing ExecutionPlan, seeing both is confusing ("which one do I override, and when?"). Long-term the trait should expose a single canonical method.

Proposal

1. Introduce a canonical entry point, e.g. replace_children(self: Arc<Self>, children, hint: ChildrenPropertiesHint) -> Result<Arc<dyn ExecutionPlan>>, where the hint encodes "same properties, reuse cache" vs "recompute".
2. Deprecate both with_new_children and with_new_children_and_same_properties with clear migration notes pointing at replace_children.
3. Migrate the ~30 in-tree ExecutionPlan impls and all direct callers to the new method.
4. After a couple of releases, drop the deprecated methods, leaving the trait with a single canonical children-replacement primitive.

The with_new_children_if_necessary helper stays the caller-facing API and internally routes to replace_children with the appropriate hint.

Why not fold this into #23332

• The mechanical migration touches ~30 files; keeping it as a separate PR lets the semantic change (fast-path skip) land first and be reviewed on its own.
• The API rename is a naming discussion worth its own review thread.

Related

• PR #23332 — semantic change this issue builds on.
• Umbrella #22555 — with_new_children_if_necessary consolidation.

cc @alamb

[JSOD11]

I'm interested in this issue. Since the migration will touch many files, do you expect the best path forward is to have this change made in a single PR or a small sequence (e.g. add the new method, change usages over to the new method preserving PlanProperties behavior, then officially deprecate the old ones)? After #23332 lands we can begin?