[clang] [clang][CodeGen] Fix MSVC ABI for classes with a deleted copy assignment operator (PR #90547)

[Max Winkler via cfe-commits]

================
@@ -1131,13 +1132,18 @@ static bool isTrivialForMSVC(const CXXRecordDecl *RD, QualType Ty,
     return false;
   if (RD->hasNonTrivialCopyAssignment())
     return false;
+  if (RD->needsImplicitCopyAssignment() && !RD->hasSimpleCopyAssignment())
----------------
MaxEW707 wrote:

Correct. The two main cases we need to cover are the following. 
I'll make a comment to explain the logic.

```
struct Test
{
    Test& operator=(const Test&) = delete;
    int x;
};
```
In this case `DefaultedCopyAssignmentIsDeleted` is `false` on the `CXXRecordDecl`. So we need to query `isDeleted` on the copy assignment operator `CXXMethodDecl`.

```
struct Test
{
    int& x;
};
```
In this case we have no `CXXMethodDecl` for the copy assignment operator so we need to check if `DefaultedCopyAssignmentIsDeleted` is `true` on the `CXXRecordDecl`.

https://github.com/llvm/llvm-project/pull/90547