Revert "Correctly handle private and public key filenames"

This reverts commit 73025de87e7ba9c16de80f61d2731342c201162e.
Revert "Add warning when dx ssh is not configured"

This reverts commit 8b703b1f8235654585d7f43666b7692dfa09b7b1.
Revert "Only test dx ssh-config on staging and production"

This reverts commit c992b32a7f54e1f84f82d44c4795f42dd5f9909b.
Revert "[PTFM-12138] Add test for dx ssh-config #resolve"

This reverts commit 5f1f79eae0180ad0bfa755e2fd5e6e46a9a1f632.
Revert "[PTFM-12040] dx ssh; dx ssh-config; dx run --ssh, --allow-ssh"

This reverts commit 14cc67212c9b8e3a387b56fbf1c4a06ed5943baa.