Update Datafusion to 49

[DerGut]

Datafusion has released version 50 in the last week. We should update iceberg-datafusion to allow integrating with the latest versions.
I will follow up with a v50 issue, but it may make sense to release one iceberg-datafusion version per datafusion to not leave anyone behind 🤷

[kevinjqliu]

Thanks for creating this!

I tested out v49 in #1639

Be careful when upgrading datafusion 49. It introduces a breaking change and is not backwards compatible with older versions.
More context: #1647 (comment)