MacOS native OpenSSH causes Terminus actions on frozen sites on Pantheon to hang

[jazzsequence]

As reported in this docs issue, Terminus will hang on MacOS if running commands on a frozen site when the host machine is using the MacOS-native version of OpenSSH. A workaround exists to just use the Homebrew version of OpenSSH, but this puts the burden of resolving the issue on the user.

Ideally, whatever we're doing in Terminus that causes the operation to hang with Mac-native OpenSSH could be fixed in Terminus and then we can remove the requirement to install OpenSSH to resolve this issue.

[stevector]

In a meeting @namespacebrian and @jazzsequence agree that a better solution would be to check if a site is frozen before attempting to connect via SSH.