[iceberg] Fix contains_nan in partition summary for float/double

[ArnavBalyan]

Purpose

• IcebergManifestFile hardcodes contains_nan = false in IcebergPartitionSummary.
• This value is used by readers for predicate pruning, hardcoding to false causes the files to get skipped that contain NaN matches.
• Detect NaN via the existing min/max and pass it correctly. Issue only emerges for float/double values.

Tests

• UT

[JingsongLi]

+1