[Iceberg] Establish a minimal e2e-tested read integration

[gabotechs]

Part of #599.

Establish the minimal native Iceberg integration that can serve as a stable foundation for follow-up work.

Scope:

• Add the datafusion-distributed-iceberg crate and register its table-provider integration.
• Support reading a static Iceberg table through SQL.
• Include a committed Iceberg fixture and integration tests that execute real SQL queries against it.
• Keep the initial implementation single-node; distributed plan serialization and scheduling improvements are follow-up work.

Acceptance criteria:

• CREATE EXTERNAL TABLE ... STORED AS ICEBERG can register the fixture.
• End-to-end tests cover scan, projection, filtering, and limits using the fixture.
• The crate is a usable base for incrementally addressing the remaining Iceberg TODOs.

[gabotechs]

Take