Feature: Enable GitHub SSH fingerprinting verification lockstep as well

[JasonYao]

The Problem

• Doing a git clone blah on a fresh machine with a proper SSH credential means trying to authenticate the validity of the serving host at github.com
• This causes you to need to trust a fingerprint that in reality people in most cases don't actually verify, opening them up to man-in-the-middle attacks

Solution

• Ideally, we could re-use the same state management logic that lockstep has for keeping allow-listed firewall rules to also manage the allow-list for SSH hosts, enabling us to remove the manual step of verification and enabling us to avoid that initial prompt in the first place