Add `validate_added_delete_files`

> Java has a `validateDeleteFileForVersion` which might be nice to have the same? https://github.com/apache/iceberg/blob/0f657edf12dc29f8487a679bfdd4210e9588d014/core/src/main/java/org/apache/iceberg/MergingSnapshotProducer.java#L295-L316

_Originally posted by @xanderbailey in [#2367](https://github.com/apache/iceberg-rust/pull/2367/changes#r3200237452)_

We should also think about guarding validations using configurable flags, so they can be skipped when needed

Start by comparing Apache Iceberg Java's MergingSnapshotProducer.validateDeleteFileForVersion implementation at the linked lines, then locate the corresponding Rust snapshot and delete-file validation entry points. Confirm the intended validate_added_delete_files behavior and whether configurable flags are required; done means the expected validation is covered and the skip behavior is settled.

Written by the indexing model from the issue text.