allow entering ssh config entry name to leverage it during ssh setup

[jace-roell]

with an ssh config (.ssh/config) like such:

Host mymainframe
  HostName example.com
  User user
  Port 22
  IdentityFile ~/.ssh/id_rsa

When running the Connect to host... command palette command and selecting + Add a new host
The user should be able to enter ssh mymainframe to leverage the above profile.

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