[Improve][Test][Connector-V2][MongoDB] Add few test cases for BsonToRowDataConverters

[loustler]

Purpose of this pull request

Add few test cases to covered as a unit test for last PR #6997 , #7567. They were improved a BsonToRowDataConverters about a double and a bigint. But I added a test case for #6997 as a e2e test case, now I felt it's too heavy for it, so I changed it to a unit test, and a new test case for #7567

It resolved this discussion

Does this PR introduce any user-facing change?

NO

How was this patch tested?

NO NEED

Check list

• If any new Jar binary package adding in your PR, please add License Notice according
  New License Guide
• If necessary, please update the documentation to describe the new feature. https://github.com/apache/seatunnel/tree/dev/docs
• If you are contributing the connector code, please check that the following files are updated:
  1. Update plugin-mapping.properties and add new connector information in it
  2. Update the pom file of seatunnel-dist
  3. Add ci label in label-scope-conf
  4. Add e2e testcase in seatunnel-e2e
  5. Update connector plugin_config
• Update the release-note.

[Hisoka-X]

LGTM. Thanks @loustler !