[clang] Reapply "[Clang][CWG1815] Support lifetime extension of temporary created by aggregate initialization using a default member initializer" (PR #97308)

[via cfe-commits]

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@@ -206,19 +206,28 @@ namespace cwg1814 { // cwg1814: yes
 #endif
 }
 
-namespace cwg1815 { // cwg1815: no
+namespace cwg1815 { // cwg1815: 19
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yronglin wrote:

Oh, I missed this! I'll fix it. Thank you for point out this.

https://github.com/llvm/llvm-project/pull/97308