[clang] Reapply "[Clang][CWG1815] Support lifetime extension of temporary created by aggregate initialization using a default member initializer" (PR #108039)

[Erich Keane via cfe-commits]

================
@@ -7810,9 +7813,11 @@ class Sema final : public SemaBase {
   }
 
   bool isInLifetimeExtendingContext() const {
-    assert(!ExprEvalContexts.empty() &&
-           "Must be in an expression evaluation context");
-    return ExprEvalContexts.back().InLifetimeExtendingContext;
+    return currentEvaluationContext().InLifetimeExtendingContext;
+  }
+
+  bool needRebuildDefaultArgOrInit() const {
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erichkeane wrote:

```suggestion
  bool needsRebuildOfDefaultArgOrInit() const {
```

https://github.com/llvm/llvm-project/pull/108039