[Analysis] Avoid virtual dtor. NFC.

Replace virtual destructor by a protected non-virtual one. Additionally also making derived structs as virtual avoids the warning from reappearing.

Also see the mailing list discussion: https://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20220516/1038290.html

Reviewed By: dblaikie, YangKeao

Differential Revision: https://reviews.llvm.org/D125830