[Hotfix][Core] Fix concurrency exceptions when MultiTableSink#PrepareCommit

[hailin0]

Purpose of this pull request

[Hotfix][Core] Fix concurrency exceptions when MultiTableSink#PrepareCommit

close #7685

Does this PR introduce any user-facing change?

No

How was this patch tested?

Add

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]

Looks like

seatunnel/seatunnel-api/src/main/java/org/apache/seatunnel/api/sink/multitablesink/MultiTableSinkWriter.java

Line 223 in 6765312

sinkWritersWithIndex

not thread safe too.

[hailin0]

sinkWritersWithIndex

@Hisoka-X
This object is read-only, Read only does not cause an concurrent exception