Engine: tables through lakekit's common table view instead of iceberg-rust #189

Spec 47. The engine loads, creates, commits to and expires tables through lakekit-table (polythings/lakekit#13, lakekit spec 5) instead of iceberg-rust:

• storage.rs's adapter for iceberg-rust's file I/O goes, and object_store reaches lakekit through loko's adapter;
• table loading, creation, the commit builder, and snapshot expiry move to lakekit;
• dedup on read takes each file's commit rank from the view.

iceberg-rust stays as the reference in interop tests. Needs: lakekit 0.1 published and #186 merged, polythings/loko#2 (Send futures), and Arrow on the newest DataFusion's major (lakekit D17).