fix for macOS: exclude IFF_POINTTOPOINT interfaces and exclude Apple P2P interfaces by default

[keepsimple1]

This is to solve issue #410.

It turns out that the root cause is mdns-sd publishes on more interfaces than Apple Bonjour (by default):

• Bonjour always excludes "point-to-point" interfaces, e.g. VPN tunnels, with flag IFF_POINTTOPOINT.
• Bonjour by default excludes Apple P2P interfaces, e.g. "awdl", "llw" unless the caller enables them.

This fix is to match what Bonjour does. In my local testing, no more conflicts for the hostname.

• Added a new API include_apple_p2p for "awdl", "llw" interfaces. By default, they are excluded.

Test

I ran the following on a Macbook where the hostname is MacBook-Air-128.local

$ cargo run --example register _skip-p2p._udp instance1 MacBook-Air-128

Verified that afterwards the hostname is still the same.