feat: native RANGE window frames with explicit offset on DATE ORDER BY

[0lai0]

Which issue does this PR close?

Part of #4834 (DATE ORDER BY only; DECIMAL remains a follow-up)

Rationale for this change

Native windows used to fall back to Spark for RANGE frames with an explicit PRECEDING / FOLLOWING offset when ORDER BY was DATE. Spark ships that offset as an integer literal, but arrow-arith rejects Date32 + Int32 and requires an Interval RHS.
This PR coerces the offset to IntervalDayTime when the ORDER BY column is Date32, so boundary math uses Date32 + IntervalDayTime and the DATE fallback can be removed. UNBOUNDED / CURRENT ROW already ran natively; DECIMAL still falls back.

What changes are included in this PR?

• Native planner : coerce Int32 / Int64 RANGE offsets to IntervalDayTime for Date32 ORDER BY.
• Scala serde : drop the DateType RANGE fallback; keep the DECIMAL fallback.
• Tests : 7 cases in CometWindowExecSuite (offsets, duplicate dates, nulls, unbounded baseline).

How are these changes tested?

./mvnw test -Dtest=none -Dsuites="org.apache.comet.exec.CometWindowExecSuite"