As part of the work on #7248 I wanted to know all of the flags on the
RouteMessage struct that we get back from macOS. Though it doesn't turn
out to be useful (when using an exit node/Tailscale is the default route,
the flags for the physical interface routes are the same), it still seems
useful from a debugging/comprehensiveness perspective.
Adds additional Darwin flags that were output once I enabled this mode.
Signed-off-by: Mihai Parparita <mihai@tailscale.com>
21fda7f670