fix: corebluetooth peripheral name

[szymonlesisz]

as well described here peripheral local_name and advertisement_name are two different things and it is justified to keep them separated as situation that local_name is not equal advertisement_name could happen in all platforms and can be implemented later as followup.

currently it is quite unfortunate that the API changes the peripheral local_name (GAP) by joining those two values

changes:

1. added Peripheral.advertisement_name - default None
2. implement advertisement_name in corebluetooth

fix: #434

[tternes]

Thank you for working on this! I should be able to do some testing this week and share feedback.

[tternes]

I finally had a chance to test this in our setup. It works exactly as expected. Really nice solution.

Thanks @szymonlesisz!