Commissioner shutdown during BLE discovery may not work very well

[bzbarsky-apple]

Problem

If a DeviceCommissioner is shut down while in the middle of doing BLE discovery for a commissioning attempt, we may end up with use-after-free, because some of our platforms don't have an obvious way to cancel BLE discovery, and when it calls back it will be touching deleted objects.

Proposed Solution

Figure out whether we can tie the BLE discovery handling to something that has long-enough lifetime and holds weak refs to the SetUpCodePairer that get nulled out as needed, or whether we can make BLE discovery be consistently cancelable.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.