Clangd doesn't find cross references to UDL

[usx95]

bool operator"" _b(unsigned long long value);
    
bool x = 1_b;

Finding references on _^b does not give any references except itself. Reference to _b in bool x = 1_b is missing.

Similarly, 1_^b gives no references at all.

[llvmbot]

@llvm/issue-subscribers-clangd

Author: Utkarsh Saxena (usx95)

```cpp bool operator"" _b(unsigned long long value);

bool x = 1_b;

Finding references on `_^b` does not give any references except itself. Reference to `_b` in `bool x = 1_b` is missing.

Similarly, `1_^b` gives no references at all.
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