feat: add native Iceberg CDC and micro-batch execution

[peterxcli]

Which issue does this PR close?

Closes #4992.

Rationale for this change

Iceberg append micro-batches and batch changelog queries cannot currently use Comet throughout their data-processing path. This adds experimental native execution while reusing Spark/Iceberg planning and recovery.

What changes are included in this PR?

• Read Spark 4.x Iceberg micro-batches using the source's offset-bounded tasks, preserving progress and checkpoint restart. Enable compatible native aggregate computation around Spark state-store boundaries.
• Read .changes tasks with the existing native Iceberg reader and process carry-over removal, update images, and net changes in Rust through create_changelog_view.
• Add opt-in configuration, documentation, and CI coverage. Retain fallback for unsupported scans, state buffers, CDC value types, and procedure closure layouts.

Spark retains offsets, persistent state, and sink commits. Streaming joins/deduplication remain in Spark. Batch CDC retains Iceberg's restriction on MOR changes involving delete manifests; this does not add a streaming CDC source.

How are these changes tested?

17 integration tests passed against Polaris and RustFS with Spark 4.1.3 / Iceberg 1.11.0. They assert native execution and Spark-equivalent results for COW V1/V2/V3 CDC, snapshot/timestamp bounds, integrity queries, and streaming checkpoint/retry behavior. The same 17 tests passed with the local catalog after rebasing onto current main. Three Rust CDC tests, Clippy, Scala formatting, and style checks also passed.