[clang] Reland [Clang] skip default argument instantiation for non-defining friend declarations to meet [dcl.fct.default] p4 (PR #115487)

[via cfe-commits]

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@@ -717,6 +717,8 @@ Bug Fixes to C++ Support
 - Clang now uses valid deduced type locations when diagnosing functions with trailing return type
   missing placeholder return type. (#GH78694)
 - Fixed a bug where bounds of partially expanded pack indexing expressions were checked too early. (#GH116105)
+- Fixed an assertion failure caused by invalid default argument substitutions in non-defining
+  friend declarations. (#GH113324).
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cor3ntin wrote:

```suggestion
  friend declarations. (#GH113324)
```

https://github.com/llvm/llvm-project/pull/115487