Implement "List requests" API feature

We want to browse the list of submitted add-forge requests so we need a dedicated API endpoint to do so.

Anonymous users should only get info about forge type, forge URL, request status and submission date.

Moderator users should get all info about a request.

Logged in users should also have the possibility to only list their requests.

Migrated from T4027 (view on Phabricator)

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