Add a sanity check for duplicate file actions in commitImpl

[dhruvarya-db]

What changes were proposed in this pull request?

This PR adds a sanity check to the commit path that rejects a commit containing duplicate file actions for the same (path, deletion vector id).commitImpl previously did not validate that the prepared actions were free of duplicates. This change adds that validation:

• A new checkNoDuplicateActions helper on the ConflictChecker companion object that streams the actions in a single pass and throws if it finds the same file added twice, the same file removed twice, or the same path + deletion vector both added and removed within one commit.
• A new error class DELTA_DUPLICATE_ACTIONS_FOUND and the corresponding DeltaErrors.duplicateActionCheckFailed helper.
• A call site in commitImpl, guarded by the DELTA_DUPLICATE_ACTION_CHECK_ENABLED configuration, that runs the check on the prepared actions before a commit is written.
• Re-validation after conflict resolution: ConflictChecker.checkConflictsAndValidateActions re-runs the duplicate check whenever conflict resolution changes the current transaction's actions.

How was this patch tested?

Added 10 tests to OptimisticTransactionSuiteBase covering duplicate add, duplicate remove, and add/remove overlap on the same path, including deletion-vector variants (same DV, DV vs. no DV, and different DVs). They run in every concrete suite that mixes in the base trait.

Does this PR introduce any user-facing changes?

No.

[felipepessoto]

@dhruvarya-db @prakharjain09 @murali-db I think it would be possible to be even more strict and disallow duplicated path regardless of DV:

Moreover, for simplicity it is required that there is at most one file action of the same type for any path (regardless of dvId)