[RootCanal] Add support for LinkPolicy and RoleChange in RootCanal

Needed for HID PTS tests. We just "fake" the link policy and our current
role by tracking them locally, rather than using LMP to coordinate with
the peer. This can be changed at a future date if a test depends on this
working.

Bug: 239986609
Test: HID PTS tests
Tag: #feature
Change-Id: I3b2b97a200b0279251fc68e37e23b8d3cfb8bdeb