feat(ssh)!: configure keys with filename and content

Accept SSH key content directly so callers no longer need role-specific
source directories. Update Molecule coverage and documentation.

BREAKING CHANGE: private_keys entries must be objects with filename and
content instead of file names. authorized_keys entries must provide
content alongside filename. Public keys are also written to ~/.ssh.

Co-authored-by: Copilot <copilot@github.com>

templates/authorized_keys.j2

@@ -21,8 +21,8 @@
     {% endif %}
   {% endif %}
   {% if _args | length > 0 %}
-{{ _args | join(',') }} {{ lookup('file', 'ssh/authorized_keys/' + authorized_key.filename ) }}
+{{ _args | join(',') }} {{ authorized_key.content | trim }}
   {% else %}
-{{ lookup('file', 'ssh/authorized_keys/' + authorized_key.filename ) }}
+{{ authorized_key.content | trim }}
   {% endif %}
 {% endfor %}