[Feature] Support writing to branch during CDC

### Search before asking

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

### Motivation

Some time, user want to sync data batchly when CDC task running. And no data overwriting is expected, which means even for the same record (identified by the PK). The late arrived CDC data could not overwrite the offline data.

### Solution

Use a dedicated fallback realtime branch for the CDC sinking.
The branch name could be provided with the following option:
```shell
--table-branch tablename=branch_name
```

### Anything else?

_No response_

### Are you willing to submit a PR?

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

The issue names no files or tests; start by locating the CDC sink and the parser for the `--table-branch` option. Done means CDC writes each configured table to its dedicated fallback branch without overwriting offline data, including records with the same primary key.

Written by the indexing model from the issue text.