[Feature] Support delete in Partial-update

### Search before asking

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

### Motivation

We use Paimon Partial-update to build a wide table, repalcing traditional multi-stream join job in Flink.
Since the multi-stream data come from different date(dt), we do not use dt as primary key.
So we hope to use insert & delete(not supported yet) Flink job at the same time to maintain the table data at 45 days.

### Solution

_No response_

### Anything else?

_No response_

### Are you willing to submit a PR?

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

Start by locating Paimon's Partial-update implementation and its Flink integration, then trace how insert operations maintain table data. Define the delete behavior needed for records arriving from multiple date partitions, including how maintaining 45 days of data should be verified.

Written by the indexing model from the issue text.