API v2 Follow-up

[dimas-b]

Follow-up work for #5112

• [ ] Update Iceberg: https://github.com/apache/iceberg/issues/6031
• [x] Conflict resolution parameters for commits.
• [x] Review and update commit information (e.g. message) created for merge + transplant operations #4430
• [x] Additional commit parents #5634
• [x] V2 is SQL tests #5663
• [ ] Add generic java client runtime exceptions #4599
• [x] Refactor NessieError and ErrorCode to become extensible #4310
• [ ] Use API v2 in UI #5410
• [x] Paginated getEnties #5448
• [ ] Support retrying idempotent operations in the HttpClient (java) #4598
• [ ] Support cachable REST responses #5111
• [ ] Evaluate usage of RevAPI #4133 (this is related, but might help to prove compatibility)
• [x] Handle relative hashes in Reference #1352
• [x] ContentKey based filter in the Nessie Diff API #3957
• [x] Pre-GA API "think-through" #1804