XWIKI-11382: DBTreeList properties don't display checkboxes in edit mode and layout is broken on flamingo.

(cherry picked from commit 4f988cf0c5e49cde15ac9d3559fbfc91f28f9f96)
XWIKI-11426: Cannot use Silk icon theme anymore.

(cherry picked from commit fd12798af6dc8e39a3da927c0683b5bb7307e0ff)