fix(pg-cdc): fix role-based permission for rds

[KeXiangWang]

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What's changed and what's your intention?

As @edeesis use his own fork to submit codes and it's troublesome for me to submit my change to his branch. I move all the changes of the original PR here. Thanks for your effort.

The changes resolve #19020.
All the credit goes to @edeesis

Checklist

• I have written necessary rustdoc comments.
• I have added necessary unit tests and integration tests.
• I have added test labels as necessary.
• I have added fuzzing tests or opened an issue to track them.
• My PR contains breaking changes.
• My PR changes performance-critical code, so I will run (micro) benchmarks and present the results.
• My PR contains critical fixes that are necessary to be merged into the latest release.

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Release note