[EPIC] Iceberg REST recoverable table deletion roadmap

### Describe the proposal

Track Apache Gravitino’s IRC-only work to make deletion of an Iceberg table recoverable for a bounded retention period, followed by reliable physical purge.

The immediate phase is design alignment and an explicit go/no-go. The implementation epics describe the expected delivery shape, but remain blocked until review accepts the API, deletion-record, and deployment decisions.

Initial scope is Iceberg tables through IRC. This roadmap does not approve general native-Gravitino metadata soft delete, other entity types, or a `table_meta`-backed architecture.

### Task list

- [ ] #12393
- [ ] #12394 *(Blocked on design go/no-go.)*
- [ ] #12395 *(Blocked on design go/no-go.)*
- [ ] #12396 *(Blocked on design go/no-go.)*
- [ ] #12397 *(Blocked on design go/no-go.)*
- [ ] #12398 *(Blocked on design go/no-go.)*

Related to: #12219, #12257, `design-docs/async-iceberg-rest-hard-deletion.md`