[clang] [NFC][analyzer] Eliminate NodeBuilder from ExprEngine visit methods and from their utility methods (PR #212186)

[Donát Nagy via cfe-commits]

================
@@ -1027,23 +1022,21 @@ void ExprEngine::VisitCXXNewExpr(const CXXNewExpr *CNE, ExplodedNode *Pred,
       // If the array is list initialized, we bind the initializer list to the
       // memory region here, otherwise we would lose it.
       if (isInitList) {
-        Bldr.takeNodes(Pred);
-        Pred = Bldr.generateNode(CNE, Pred, State);
+        Pred = Engine.makePostStmtNode(CNE, State, Pred);
 
         SVal V = State->getSVal(Init, SF);
         ExplodedNodeSet evaluated;
         evalBind(evaluated, CNE, Pred, Result, V, true);
 
-        Bldr.takeNodes(Pred);
-        Bldr.addNodes(evaluated);
+        Dst.insert(evaluated);
----------------
NagyDonat wrote:

The code after this point clearly assumes that `evaluated` contains exactly one element and will erase that element from `Dst`, so there is no need to insert `evaluated` into `Dst` but it would be nice to check this assumption with an assertion:
```suggestion
        assert(evaluated.size() == 1);
```

Also please check the source code of `evalBind` to see whether this assertion is justified, and if not, refactor the logic to gracefully handle other `size()` as well.

(In particular think about the possibility of a corner case where we generate a `PosteriorlyOverconstrained` node which is a sink and therefore isn't inserted into a node set -- and determine whether `*evaluated.begin()` could crash in that case.)

https://github.com/llvm/llvm-project/pull/212186