[clang][ExprConst] Add "declared here" notes to uninitialized read diagnostics (#192206)

E.g. for

```c++
constexpr int unInitLocal() {
  int a;
  return a; // both-note {{read of uninitialized object}}
}
static_assert(unInitLocal() == 0, ""); // both-error {{not an integral constant expression}} \
                                       // both-note {{in call to 'unInitLocal()'}}
```

we now diagnose:
```console
array.cpp:896:15: error: static assertion expression is not an integral constant expression
  896 | static_assert(unInitLocal() == 0, ""); // both-error {{not an integral constant expression}} \
      |               ^~~~~~~~~~~~~~~~~~
array.cpp:894:10: note: read of uninitialized object is not allowed in a constant expression
  894 |   return a; // both-note {{read of uninitialized object}}
      |          ^
array.cpp:896:15: note: in call to 'unInitLocal()'
  896 | static_assert(unInitLocal() == 0, ""); // both-error {{not an integral constant expression}} \
      |               ^~~~~~~~~~~~~
array.cpp:893:7: note: declared here
  893 |   int a;
      |       ^
1 warning and 1 error generated.
```
and point at the object that we were trying to read from. This adds an
`NoteLValueLocation()` call to the emission of
`note_constexpr_access_uninit`, which is already done in other places:


https://github.com/llvm/llvm-project/blob/7ae5fe63dd979eae13ea04e166f94056ec1306ca/clang/lib/AST/ExprConstant.cpp#L4565-L4570