pad: Check if events need to be resent after IDLE probes

Otherwise it might happen that when relinking happens in an IDLE probe after forwarding the CAPS event, that the CAPS event is only forwarded to the previous peer but not to the new peer. Afterwards the new peer will handle buffers that are according to different caps than the ones configured.

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I'll clean this up into multiple commits later and also write a test for it and similar situations