Add support for writing partitionValues_parsed field in Delta Lake checkpoint

[ebyhr]

https://github.com/delta-io/delta/blob/master/PROTOCOL.md#checkpoints-1

partitionValues_parsed: In this struct, the column names correspond to the partition columns and the values are stored in their corresponding data type. This is a required field when the table is partitioned and the table property delta.checkpoint.writeStatsAsStruct is set to true. If the table is not partitioned, this column can be omitted. For example, for partition columns year, month and event with data types int, int and string respectively, the schema for this field will look like: