fix: Listing block default summary should use ul tag for its listing

[ana-oprea]

This PR continues the work from PR #4994, which is now outdated. To ensure progress on the development, I've opened this new PR to carry the changes forward and address any remaining tasks or updates.

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[ichim-david]

@plone/volto-accessibility we need to have a look at this change and provide feedback

[ichim-david]

@JeffersonBledsoe never mind the review request there needs to be some changes done to this pull request, one of them being not reintroducing Semantic-ui component within the Summary Template

[ichim-david]

@ana-oprea there are a couple of issues currently:

1. the listing gets empty p tag even when no content is found (no description added for item)
2. the listing also affects the coloring which might only be of importance for editors and otherwise
   confusing for anon users and wonder why there are blue or black titles
3. it's using again semantic ui react which we want to avoid adding back into core and would be better
   to use simple html elements
4. It's fair that we should avoid using headings for the listing even though classic uses h2, it should be
   something like .listing-header

[sneridagh]

@ana-oprea Thanks for removing SemanticUI fromt here! However, I won't remove the current .ui.list CSS, since you could break a lot of projects out there.
Just add the new one instead. Also, we need an upgrade guide entry since it's a breaking change in HTML of the component.