BUGFIX: Finalise and deprecate site creation module for Neos 9.0

[mhsdesign]

Resolves: #4719

In #5139 i removed the capabilities to create composer packages via web request which is now obsolete as we have the new CLI / Web setup: #4243

Now we can also reimplement 'import site' based on new SiteImportService from #5307 - the thing is this comes with some limitations like in use with CLI:

• as proposed here Discussion improve site entity and site node relation #4470 (comment) the site must have a field to define the contentRepositoryId. In the current state we can only know via the to be created site name plus the site configuration in Neos.Neos.sites via its name or the fallback * which is the 'destined' content repository.

• a current limitation of the setup is that it can really only be executed once. After the events are set deleting the site (soft, without pruning the cr) a reimport would just duplicate the events again which is not the desired step probably. For that we allow to prune the site via flow cr:pruneAll. Those steps are to be used with care and not available via GUI.

The advantage CLI gives us is that for example failures in the done replay and all other steps are not obscured and can easily be be debugged. Also for managing multiple content repositories or changing dimensions configuration changes have to be undertaken which is closer to CLI.

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• Code follows the PSR-2 coding style
• Tests have been created, run and adjusted as needed
• The PR is created against the lowest maintained branch
• Reviewer - PR Title is brief but complete and starts with FEATURE|TASK|BUGFIX
• Reviewer - The first section explains the change briefly for change-logs
• Reviewer - Breaking Changes are marked with !!! and have upgrade-instructions