feat: Expose Iceberg table statistics in DataFusion interface(s)

[gruuya]

At present the two key DataFusion interfaces for Iceberg lack statistics information, as they rely on default (i.e. missing/unknown) implementations for TableProvider::statistics and ExecutionPlan::statistics.

These can be quite important (particularly the later one) during join planning, as DataFusion uses a number of heuristics that are based on these stats when planning joins, and so they can impact performance.

[gruuya]

I'd be happy to work on developing this.

[Xuanwo]

Thank you a lot for working on this!