feat: support sort_array expression

[grorge123]

Which issue does this PR close?

Closes #3159.

Rationale for this change

Currently, comet does not support sort_array expression, so using sort_array(...) would fall back to Spark. This PR adds sort_array support to achieve native acceleration.

The SortArray expression sorts the elements of an array in either ascending or descending order.

What changes are included in this PR?

• Add CometSortArray in arrays.scala to serialize Spark SortArray as DataFusion array_sort.
• Register SortArray in QueryPlanSerde.scala.
• Preserve Spark sort semantics:
  • sort_array(arr) / sort_array(arr, true) -> ascending with NULLS FIRST
  • sort_array(arr, false) -> descending with NULLS LAST
• Mark floating-point array sorting as Incompatible only when spark.comet.exec.strictFloatingPoint=true.
• Explicitly reject unsupported nested complex cases such as array<array<struct<...>>> at planning time so they cleanly fall back to Spark instead of failing at runtime.
• Update the supported-expression documentation in spark_expressions_support.md.

How are these changes tested?

• Added SQL-file coverage in sort_array.sql for:
  - array
  - array
  - array including NaN, -0.0, and 0.0
  - array<decimal(10,0)>
  - array
  - array<struct<...>>
  - array<array>
  - array literal case
  - empty arrays
  - null arrays
  - explicit ascending / descending paths
  - literal and table-column inputs

Reference: https://github.com/apache/spark/blob/04b821c69e85be5f51a1270b3a9a4155afdb5334/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/CollectionExpressionsSuite.scala#L706-L760