[clang] [HLSL] Implement the dst HLSL Function (PR #133828)

[Farzon Lotfi via cfe-commits]

================
@@ -35,6 +35,12 @@ length_vec_impl(vector<T, N> X) {
 #endif
 }
 
+template <typename T>
+constexpr vector<T, 4> dst_impl(vector<T, 4> Src0, vector<T, 4> Src1) {
+  vector<T, 4> Dest = {1, Src0[1] * Src1[1], Src0[2], Src1[3]};
+  return Dest;
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farzonl wrote:

```suggestion
  return  {1, Src0[1] * Src1[1], Src0[2], Src1[3]};
```

https://github.com/llvm/llvm-project/pull/133828