Kafka Connect: auto create with lowercase columns

[bryanck]

Feature Request / Improvement

Currently when auto create is enabled, the sink will create tables with column names using the original case in the record schema (or record if not using a schema). We should add an option to force column names to lower case, to avoid case-sensitivity issues.

See: https://apache-iceberg.slack.com/archives/C03SEK9PW0Z/p1725468165932919

Query engine

Kafka Connect

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