Fixes an issue with a confusing error: "paramiko: The authenticity of host '[host]' can't be established" when ssh on the command line doesn't complain
Closes PR #7730
Also making PlayContext a child class of the Playbook Base class,
which gives it access to all of the FieldAttribute code to ensure
field values are correctly typed after post_validation
Fixes#11381
Moving the make_sudo_cmd() calls back up to the action level so that connection
plugins don't have to know about it at all, and moving some of the become data
(prompt and success_key) into the ConnectionInformation object so they don't
need to be passed around needlessly.
