Initial ansible_ssh_proxy support for ssh transport

This pull request adds functionality to supply a host to use with the SSH ProxyCommand as requested in #8963

Currently this only:

1. Adds support for the `ssh` transport
1. Only accepts an IP or hostname, not the full ProxyCommand (The ProxyCommand utilizes `ssh -W`)
1. Only keys off of `ansible_ssh_proxy` as a "global" var (--extra-vars/vars_files/etc...) or from inventory (group_vars and host_vars included)