[Feature] flink database sync action should support merging different tables in the same database into one paimon table.

### Search before asking

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

### Motivation

When I have three tables tablea_1, tablea_2, tableb in a database and I use flink database sync, I hope to merge tablea_1 tablea_2 into one paimon table.

### Solution

Add configuration in Synchronizing Databases for full database synchronization
`--merge_tables='tablea_1|tablea_2'`
`--paimon_merge_table_name = 'tablea'`

### Anything else?

_No response_

### Are you willing to submit a PR?

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

Start by locating the Flink database sync action and the “Synchronizing Databases” configuration described in the issue. Determine how merging tablea_1 and tablea_2 into the configured tablea should be represented, and verify that the requested configuration works without changing unrelated tables.

Written by the indexing model from the issue text.