[clang] [clang][Sema] Recheck array size once the element type is complete (PR #219817)

[Erich Keane via cfe-commits]

https://github.com/erichkeane commented:

How does this prevent multiple diagnostics for non-dependent things in a dependent context?  WE probably need a test for something like that:
```
template<typename T>
struct Parent {
double Array[4294967173u];
};
Parent<int> p;
```

Also, the diagnostic isn't a good one?  It seems to imply that the problem is that the array has too many elements, but we dont' diagnose that with incomplete types.  In reality, this is complaining that there are too many BYTES right?  The diagnostic needs to be better fit to the actual problem.

https://github.com/llvm/llvm-project/pull/219817