[Fix][Flink] Fix NPE when get null row from upstream transform

[litiliu]

Purpose of this pull request

This close #8468
This PR adds a filter operator to filter the null rows generated by the transform plugins. It's easier than adding the null check in every transform plugin.

Does this PR introduce any user-facing change?

How was this patch tested?

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 if ci passes. Thanks @litiliu

[Hisoka-X]

Please add test case in

seatunnel/seatunnel-e2e/seatunnel-transforms-v2-e2e/seatunnel-transforms-v2-e2e-part-1/src/test/java/org/apache/seatunnel/e2e/transform/TestFilterRowKindIT.java

Line 28 in adb656e

public class TestFilterRowKindIT extends TestSuiteBase {

[Hisoka-X]

LGTM if ci passes.