Revert "Refactor lavel filter to use labelName attr"

Purpose of revert

Reported in slack (internal) that label filters were not working

The backend is expecting the name (not id) in the labelName param.

However, the backend currently supports both labelName and labels so reverting will restore the label filter functionality

how to test

1. enable elasticsearch for gdk
2. label a few issues
3. do an issue search without a label filter
4. add a label filter
5. ensure the the search results are filtered by the selected label

not filtered

filtered

Checklist

• Create an issue to reinstate the merge request and assign it to the author of the reverted merge request.
• [-] If the revert is to resolve a broken 'master' incident, please read through the Responsibilities of the Broken master resolution DRI.
• [-] If the revert involves a database migration, please read through Deleting existing migrations.
• Add the appropriate labels before the MR is created. We can skip CI/CD jobs only if the labels are added before the CI/CD pipeline is created.

Milestone info

• I am reverting something in the current milestone. No changelog is needed, and I've added a ~"regression:*" label.
• I am reverting something in a different milestone. A changelog is needed, and I've removed the ~"regression:*" label.

Related issues and merge requests

!156316 (merged)