feat: create partition provide option to user to pass the partition name

[subkanthi]

For truncate partitions, the API allows an option to pass a custom name for partition. It might be useful for cases where they want to avoid the default _day, _week` names added to the col names.

    private Builder truncate(Types.NestedField sourceColumn, int width, String targetName) {
      checkAndAddPartitionName(targetName);
      fields.add(
          new PartitionField(
              sourceColumn.fieldId(), nextFieldId(), targetName, Transforms.truncate(width)));
      return this;
    }