Allow DELETE for stale externally managed ICs through API

As discussed here web#361 (closed), the DELETE endpoint of ICs should allow the deletion of externally managed ICs if these are stale (= no update for at least XX minutes).

Steps:

introduce parameter to configure stale time XX minutes
check stale time in DELETE endpoint for externally managed ICs
- if stale && not used in component config: DELETE IC and return 200
- else: return error

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