[clang][Diagnostics] Provide source range to constexpr function diags (#69721)

Before:
```console
./array.cpp:290:16: error: constexpr function never produces a constant expression [-Winvalid-constexpr]
  290 | constexpr void neverValid() {
      |                ^
./array.cpp:291:3: note: subexpression not valid in a constant expression
  291 |   throw;
      |   ^~~~~
```

After:
```console
./array.cpp:290:16: error: constexpr function never produces a constant expression [-Winvalid-constexpr]
  290 | constexpr void neverValid() {
      |                ^~~~~~~~~~
./array.cpp:291:3: note: subexpression not valid in a constant expression
  291 |   throw;
      |   ^~~~~
```