Add unused imports check/fix for Scala Code

[jackylee-ch]

Feature Request / Improvement

This is in addition to issue #7695 . As mentioned in PR #14311 , there is currently no mechanism to detect or fix unused imports, and it also canot be done in spotless. To address this issue, we will first introducing a Scala compiler option to check for unused imports, and then consider integrating Scalafix to automatically clean up unused imports.

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