[MoveOnly] Track inst-consumed bits in same SBV.

Previously, whenever an instruction was recorded as a final consume, a
new entry was added to finalBlockConsumes.  Here, this is changed to add
the new bits being consumed by the instruction to the preexisting
SmallBitVector, if there is one.

Author: nate-chandler

lib/SILOptimizer/Mandatory/MoveOnlyAddressCheckerUtils.cpp

@@ -1382,6 +1382,12 @@ struct ConsumeInfo {
       iter = finalBlockConsumes.insert({block, {}}).first;
     }
     LLVM_DEBUG(llvm::dbgs() << "Recorded Final Consume: " << *inst);
+    for (auto &pair : iter->second) {
+      if (pair.first == inst) {
+        pair.second |= bits;
+        return;
+      }
+    }
     iter->second.emplace_back(inst, bits);
   }