Permission policy needs to be checked when owner set changes

[kenchris]

I will assume that it is quite common that a site using shared workers, will create the worker, then turn on compute pressure in that worker, and then when additional same origin sites are loaded, they will connect to the shared worker.

As currently spec'ed, even if the second site doesn't have appropriate permission policy set, it will be able to receive telemetry data as we only check the permission policy when we start observing.

There doesn't look to be any nice hooks to hook into when owner set changes so we might need to monkey patch