private static NameMapping convertToLowercase(NameMapping nameMapping) {
    return NameMapping.of(convertToLowercase(nameMapping.asMappedFields().fields()));
  }
Create a new NameMapping with the same names but converted to lowercase.

@param nameMapping The original NameMapping, potentially containing non-lowercase characters
amoro-format-mixed/amoro-mixed-trino/src/main/java/org/apache/amoro/trino/unkeyed/IcebergPageSourceProvider.java