I'm working on moving all network state queries to be on
netmon.Monitor, removing old APIs.
Updates tailscale/corp#10910
Updates tailscale/corp#18960
Updates #7967
Updates #3299
Change-Id: If0de137e0e2e145520f69e258597fb89cf39a2a3
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>