Bluetooth: move to controller-based privacy only

[jori-nordic]

Problem

The Zephyr host currently implements Bluetooth LE privacy.
This was implemented back when the open-source controller didn't support controller-based privacy.
This has now changed, the controller now fully supports privacy.

Unfortunately, parts of the Host-based privacy are un-implementable, by spec. So for these parts we have to use controller privacy (which we do).
This makes the code unnecessarily hard to maintain, and nullifies potential gains from hardware accelerators on the controller.

Solution

Remove host-based privacy in favor of controller-based privacy.

Alternatives

Keep using host-based privacy and:

• Remove support for operations that are not possible with it
• Add support for hardware accelerators. Probably need a whole new driver spec for this.

[rugeGerritsen]

Note: If the support for host-based privacy is removed, the resolving list size in the controller will be the limiting factor. The current host implementation allows the application to use more stored identities than what can be stored in the resolving list in the controller.