Add info about implemented connection details to Github issues

There exist several issues about wanting to access connection details for instance testing etc. (at least https://github.com/hashicorp/packer/issues/3331 https://github.com/hashicorp/packer/issues/3889 https://github.com/hashicorp/packer/issues/4173) which are all closed and locked.
Meanwhile, the needed connection informations (Host=IP, Port, User, Password...) are available to provisioners: https://developer.hashicorp.com/packer/docs/templates/hcl_templates/contextual-variables.
Please add comments to these issues pointing to the up to date documentation so the infos get found when doing an internet search.

Open issues 3331, 3889, and 4173, then review the linked Packer contextual-variables documentation. First verify whether comments can be added to the closed and locked issues. Done means the target issues point to the current documentation for Host, Port, User, and Password, with the links checked.

Written by the indexing model from the issue text.