Use this in the default migration to Volto

I want to switch the default migration to Volto (as documented in https://6.docs.plone.org/backend/upgrading/version-specific-migration/migrate-to-volto.html and in https://github.com/collective/collective.exportimport?tab=readme-ov-file#migrate-to-volto) from blocks-conversion-tool to this.

The conversion is called in https://github.com/plone/plone.volto/blob/main/src/plone/volto/browser/migrate_richtext.py#L110

We could simply change the documentation to use of the docker image of `collective.html2blocks` or run it as a service but I wonder if we want to consider adding it as a dependency to `plone.volto` so we can call it directly like `collective.transmute` does. But that is at least blocked by the hard dependency on `FastAPI` and `typer`. Would it make sense to make these optional dependencies?

Start at src/plone/volto/browser/migrate_richtext.py#L110 and read the linked migration documentation and collective.exportimport README. Compare the current blocks-conversion-tool path with using collective.html2blocks, including the Docker/service and dependency options mentioned. Done means the default migration uses this tool and the FastAPI and typer dependency decision is resolved.

Written by the indexing model from the issue text.