Add help topic about installing site from configuration

For the feedback on the MR.

Thank you for working on this @martin mayer.

For you, or anyone else working on this, please refer to the proposed resolution in the issue summary as well as the Help Topics Standards → doc.

For help topics, we like to split up topics into "concepts" (usually has "overview" in the title or filename) and "tasks" (step-by-step instructions on how to do a certain task). Which means, we don't want to introduce step-by-step instructions into a concept (aka "overview") topic. But rather, add a task topic with steps, and then link to it from the related concept/overview tutorial.

So for this issue, what we need is an update to the Help module's concept topic (core.config_overview.html.twig) that describes at a high level that it is also possible to install a site from existing configuration, which bypasses the need to discover a site's UUID.

And then we need a new help topic in core/modules/help/help_topics called something like core.config_install.html.twig that has step-by-step instructions on installing an existing site from configuration, including any limitations (such as those described in 🐛 Allow an install hook in profiles installing from configuration Needs work ).

Then in both core.config_overview.html.twig and the new topic, update the related topics to include links to each other.

I realize that there is limited documentation on this task, and that the best (only?) way to accomplish it is through Drush. If that is the case, in an "Additional resources" section, add a link to this User Guide page on additional tools: https://www.drupal.org/docs/user_guide/en/install-tools.html. For any Drush commands, wrap them in HTML <code> tags.

Updated IS with link to Help Topic Standards doc.