[ASDF Role] Add asdf_plugin_dependencies

[marcus-grant]

Because there's so many plugins and I can't cover them all in this role, an extra variable asdf_plugin_dependencies should be included, expected as a list, to let role users add them in explicitly to ensure that any asdf plugin that is not covered by this role can have its dependencies installed.

[marcus-grant]

Also handle actually installing plugins as a dictionary item for each plugin install covering...

• The plugin
• The version for the runtime of that plugin
• A global default version

[marcus-grant]

Closed with 3d27872