-preview=bitfields: Bit field address escapes through `ref`

## Georgy Markov reported this on 2023-11-27T14:24:13Z

### Transferred from https://issues.dlang.org/show_bug.cgi?id=24263

### CC List

* Nick Treleaven (@ntrel)

### Description

````markdown
struct S {
    ubyte _x:4, _y:4;
    ubyte* p() => &_x;   // Error: cannot take address of bit-field `_x`
    ref ubyte x() => _x; // Compiles
}
````