DeadObjectElimination: handle OSSA instructions when analyzing class destructors

Handle typical patterns which are generated by SILGen.

lib/SIL/Utils/InstructionUtils.cpp

@@ -172,6 +172,7 @@ SILValue swift::stripCasts(SILValue v) {
     if (auto *svi = dyn_cast<SingleValueInstruction>(v)) {
       if (isIdentityPreservingRefCast(svi) ||
           isa<UncheckedTrivialBitCastInst>(v) || isa<MarkDependenceInst>(v) ||
+          isa<UncheckedOwnershipConversionInst>(v) ||
           isa<BeginAccessInst>(v)) {
         v = cast<SingleValueInstruction>(v)->getOperand(0);
         continue;