This adds a method to wgengine.Engine and plumbed down into magicsock
to add a way to get a type-safe Tailscale-safe wrapper around a
wireguard-go device.Peer that only exposes methods that are safe for
Tailscale to use internally.
It also removes HandshakeAttempts from PeerStatusLite that was just
added as it wasn't needed yet and is now accessible ala cart as needed
from the Peer type accessor.
None of this is used yet.
Updates #7617
Change-Id: I07be0c4e6679883e6eeddf8dbed7394c9e79c5f4
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
69f4b4595a