refs #17934 [finc] show site facet groups as html listings

* for more or less facets buttons: stop parent event handling on link by event.stopImmediatePropagation()
* facet group on single page: add ul
* remove filters (side facets) as list
* put scss into separate scss file in finc-accessibility theme
* inherit scss from finc-accessibility theme
* move potential PR SCSS to finc-accessibility
* small refactoring on single-facet.phtml