Merge branch '14284-allow-all-deploy-keys-to-be-retrieved-via-api-regardless-of-project-affiliation' into 'master'

Add /deploy_keys API to retrieve all deploy keys regardless of project affiliation

## What does this MR do?

Add /deploy_keys API to retrieve all deploy keys regardless of project affiliation

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

Is documentation clear?

## Why was this MR needed?

User request

## What are the relevant issue numbers?

#14284

See merge request !4426