[help] Using Java-API to implement incremental reading between Snapshots

### Search before asking

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

### Motivation

I want to implement incremental data reading of snapshots using the Java-API. I wrote a little bit myself, but I have a few questions to answer.
1. Can I only read the deltaManifest file of a snapshot of type APPEND?
2. If not, how should I handle a large amount of old data (INSERT) in a COMPACT type?
3. If possible, I would like to learn how Flink implements it(incremental-between), but I can't find any relevant documentation.

### Solution

_No response_

### Anything else?

_No response_

### Are you willing to submit a PR?

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

Start with the Java API and the snapshot-reading behavior described in the issue, then compare APPEND and COMPACT snapshots and their deltaManifest files. Review how Flink handles incremental-between, if that implementation is available in the repository. Done means the supported approach for incremental reads and handling old INSERT data is documented clearly.

Written by the indexing model from the issue text.