Native engine panics on all-scalar inputs for hour, minute, second, unix_timestamp #3336

Description

When Spark's ConstantFolding optimizer rule is disabled, all-scalar (literal-only) expressions reach Comet's native engine instead of being folded at plan time. The native engine panics with messages like:

• hour(scalar) should be fold in Spark JVM side.
• minute(scalar) should be fold in Spark JVM side.
• second(scalar) should be fold in Spark JVM side.
• unix_timestamp(scalar) should be fold in Spark JVM side.

How to Reproduce

Disable constant folding and run an all-literal datetime extraction query:

SET spark.sql.optimizer.excludedRules=org.apache.spark.sql.catalyst.optimizer.ConstantFolding;
SELECT hour(timestamp('2024-01-15 12:30:45'));

Expected Behavior

The native engine should handle scalar inputs gracefully — either by computing the correct result or by falling back to Spark, not by panicking.

Affected Expressions

• hour()
• minute()
• second()
• unix_timestamp()