Add changelog for v11.9.1 & v11.9.2

What does this MR do?

Add changelog for v11.9.1 & v11.9.2

Why was this MR needed?

Changelog is missing on master branch but is in 11-9-stable branch

Are there points in the code the reviewer needs to double check?

Does this MR meet the acceptance criteria?

• Documentation created/updated
• Added tests for this feature/bug
• In case of conflicts with master - branch was rebased