`@bitCast` allowed to cast to/from vectors of pointers

### Zig Version

0.12.0-dev.2711+f995c1b08

### Steps to Reproduce and Observed Behavior

```zig
test {
    _ = @as(@Vector(1, *u8), @bitCast(@Vector(1, usize){1}));
}
```
this test passes as well as the inverse operation

### Expected Behavior

regular pointers cannot be `@bitCast`ed, instead requiring either `@ptrFromInt` or `@intFromPtr`, vectors should behave the same