[clang] [clang-tools-extra] Reland [clang][Sema, Lex, Parse] Preprocessor embed in C and C++ (PR #95802)

[Mariya Podchishchaeva via cfe-commits]

Fznamznon wrote:

I'm trying to insert a cast using emitCast:
```
--- a/clang/lib/AST/Interp/ByteCodeExprGen.cpp
+++ b/clang/lib/AST/Interp/ByteCodeExprGen.cpp
@@ -1347,6 +1347,13 @@ bool ByteCodeExprGen<Emitter>::visitInitList(ArrayRef<const Expr *> Inits,
     }

     auto Eval = [&](Expr *Init, unsigned ElemIndex) {
+      auto ArrayTy = Ctx.getASTContext().getAsConstantArrayType(T);
+      std::optional<PrimType> FromT = classify(Init->getType());
+      std::optional<PrimType> ToT = classify(ArrayTy->getElementType());
+      if (FromT != ToT) {
+        if (!this->emitCast(*FromT, *ToT, Init))
+          return false;
+      }
       return visitArrayElemInit(ElemIndex, Init);
     };
```
But it fails with an assertion
```
source/llvm-project/clang/lib/AST/Interp/InterpStack.h:46: T clang::interp::InterpStack::pop() [with T = clang::interp::Integral<8, false>]: Asserti
on `ItemTypes.back() == toPrimType<T>()' failed.
```

https://github.com/llvm/llvm-project/pull/95802