HTTP/3: handled insertion reference to a going to be evicted entry. As per RFC 9204, section 3.2.2, a new entry can reference an entry in the dynamic table that will be evicted when adding this new entry into the dynamic table. Previously, such inserts resulted in use-after-free since the old entry was evicted before the insertion (ticket #2431). Now it's evicted after the insertion. This change fixes Insert with Name Reference and Duplicate encoder instructions.