Tls libtrust auth

Turns on TLS by default and uses public keys to authenticate access.

- This PR still may require further testing and input on the user experience.
- FSNotify support has not been added to detect changes to authorized_keys
- Depends on #8112

@bfirsh please review and comment on whether this is missing anything needed
@vieux  seems the flag is not used, just the variable.  This could definitely be cleaned up.