cli: use openssl for all crypto-related activities

For compliance with SDL and MSFT crypto standards. Right now this uses
our forks of russh and secret-service. russh seems amenable to getting
this merged (https://github.com/warp-tech/russh/pull/52) but TBD about
the secret-service crate.

Fixes https://github.com/microsoft/vscode-internalbacklog/issues/3158