Improve error logging in Kafka Connect partition spec

[aka-peter]

Feature Request / Improvement

The exception will never be logged int the error message when the partition spec is invalid (the exception instance is just an argument to the formatter and will be ignored).

https://github.com/apache/iceberg/blob/main/kafka-connect/kafka-connect/src/main/java/org/apache/iceberg/connect/data/IcebergWriterFactory.java#L96

Query engine

None

Willingness to contribute

• I can contribute this improvement/feature independently
• I would be willing to contribute this improvement/feature with guidance from the Iceberg community
• I cannot contribute this improvement/feature at this time