[Bug] Downgrade issue

### Search before asking

- [X] I searched in the [issues](https://github.com/apache/pulsar/issues) and found nothing similar.

### Version

I'm trying to downgrade from 3.0.2 to 2.10.4

### Minimal reproduce step

I'm using Kubernetes and I've deployed Pulsar with Helm. Pulsar works fine with 3.0.2 but I want to try the procedure to downgrade to 2.10.4 (in case of emergency).

### What did you expect to see?

I expect that Pulsar downgrade works

### What did you see instead?

Bookkeepers cannot start and from the logs I see:
java.io.IOException: Error open RocksDB database
Caused by: org.rocksdb.RocksDBException: **unknown checksum type 4** in /pulsar/data/bookkeeper/ledgers/current/ledgers/000006.sst offset 929 size 32

### Anything else?

Zookeeper and brokers seem to run correctly

### Are you willing to submit a PR?

- [ ] I'm willing to submit a PR!

Reproduce the downgrade from Pulsar 3.0.2 to 2.10.4 using Kubernetes and Helm, then start with the BookKeeper startup logs showing the RocksDB checksum error. Determine whether the downgrade is supported and what causes BookKeeper to reject the existing ledger data; done means the downgrade completes and BookKeeper starts successfully.

Written by the indexing model from the issue text.