fix: hash NullType and ANSI interval values natively - #7084

Which issue does this PR close?

Closes #7063.

Rationale for this change

The native Murmur3 and xxHash64 kernels had no arm for Null, Interval(YearMonth) or Duration(Microsecond), so hash(a, null), xxhash64(a, null) and native round-robin shuffle over those types failed with Unsupported data type in hasher.

What changes are included in this PR?

• create_hashes_internal! hashes Interval(YearMonth) as an int and Duration(Microsecond) as a long, as Spark does for YearMonthIntervalType and DayTimeIntervalType, and leaves the hash unchanged for Null. This covers both the hash expressions and round-robin partitioning, since they share the kernel.
• child_with_parent_nulls now returns a Null child as is. Without that, hashing a null struct that has a NullType field still panicked once the Null arm was in place, because a NullArray can't carry a null buffer (NullArray data should not contain a null buffer).

I left hash.scala alone, so hash/xxhash64 over the ANSI interval types still fall back to Spark. Enabling them there could be a follow-up now that the kernel handles them.

How are these changes tested?

New unit tests in murmur3.rs and xxhash64.rs: both interval types hash to the same values as the existing Int32/Int64 cases, and a Null column or a NullType struct field (including under a null struct) leaves the hash unchanged. A unit test in struct_nulls.rs covers the Null child. I ran the native tests for the two changed crates; I did not run the Spark/JVM suites.

AI disclosure: the change, the tests and this description were written with an AI coding assistant.