API endpoint for group owners to list all the PersonalAccessTokens in system

This API endpoint will list all the PersonalAccessTokens in system.

1. We will namespace this endpoint to /manage to indicate this is a priviledged endpoint
2. This endpoint will only list all the PersonalAccessTokens in the system and not the GroupAccessTokens or ProjectAccessTokens.
3. We will have a separate endpoint to list down all the resource access tokens or group/project access tokens for group owners