floss: Improve bonding procedure

Improve bonding in both the stack and client by doing a few things:
* Don't automatically accept pairing and let the client handle bonding.
* Client handles consent based bonding by accepting locally initiated
  bonding.
* Keep track of client initiated bonding
* Add stack apis: set_pin, set_passkey, and set_pairing_confirmation

Bug: 196887009
Tag: #floss
Test: btclient bond with consent and passkey notification
Change-Id: I6f6845d1af92e5cd10349c3bdb0b18183430b47f