make_date under a codegen-dispatched parent falls back to Spark since #7261 #7284

Describe the bug

Since #7261, a make_date under an expression that Comet runs through the codegen dispatcher falls back to Spark, and the whole operator holding it leaves Comet. Before #7261 the same expressions stayed in Comet.

CometMakeDate.unsupportedParentReason walks the parents of every make_date, and any multi-child parent it does not list ends in the default arm ("Other native multi-child expressions may evaluate operands that Spark skips"):

That covers dispatched parents such as AddMonths and MonthsBetween. A dispatched parent never runs the native make_date, though. CometCodegenDispatch binds the whole subtree and runs Spark's own generated code for it, so the make_date under it is evaluated by Spark with Spark's short-circuiting:

Results are the same either way; only the operator moves back to Spark.

Steps to reproduce

On main (967d09b), Spark 4.1 and 3.5, default configuration:

CREATE TABLE md_parent(y INT, m INT, d INT, dt DATE) USING parquet;
INSERT INTO md_parent VALUES
  (2024, 1, 31, DATE '2024-03-15'), (NULL, 2, 1, NULL), (2024, NULL, 1, DATE '2023-12-01');

SELECT add_months(dt, 1) FROM md_parent;                     -- stays in Comet (dispatched)
SELECT add_months(make_date(y, m, d), 1) FROM md_parent;     -- falls back
SELECT months_between(make_date(y, m, d), dt) FROM md_parent; -- falls back

The second query plans as:

Project [COMET: make_date requires Spark evaluation under AddMonths]
+- CometColumnarToRow
   +- CometNativeScan parquet spark_catalog.default.md_parent

and the third falls back with make_date requires Spark evaluation under MonthsBetween. On f1121ca, the commit before #7261, all three queries pass expect_dispatch in CometSqlFileTestSuite.

Expected behavior

A make_date under a parent that the codegen dispatcher will take stays in Comet, as it did before #7261. One way: have the walk stop at a parent whose serde is a CometCodegenDispatch while spark.comet.exec.scalaUDF.codegen.enabled is on, since that subtree runs as Spark code. Natively evaluated parents keep their current checks.

Additional context

Found while merging main into #5864, which adds more dispatched datetime parents (DateAddInterval, DateAddYMInterval, SubtractDates, SubtractTimestamps, TimestampAddYMInterval); a make_date under any of them falls back the same way.

@pingzh, this follows from #7261. Would you like to take it?