Only add matching roles for code owner role approvers

What does this MR do and why?

In #282438 (comment 2239115122) it was discovered that code owner role approvers were being populated across multiple entries.

In this MR we fix this so we only add roles which are found in the extractor.

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Before	After

How to set up and validate locally

1. Enable the codeowner_role_approvers feature flag.
2. Create a new project and add a separate user each for developer and maintainer.
3. Enable the codeowner switch for the main branch in settings/repository under protected branches.
4. Create a CODEOWNERS file in the root of the project.
5. Create two files called 'developer_file' and 'maintainer_file' respectively in the root of the project.
6. In the CODEOWNER file add:

developer_file @@developers
maintainer_file @@maintainers

7. Create a new merge request with changes targeting both developer_file and maintainer_file.
8. Notice that approval is required from your developer user for the develope_file and from the maintainer user for the maintainer file.

Related to #282438 (closed)