[Issue 24095] New: std.bitmanip.bitfields no longer works with bool enum types

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=24095

          Issue ID: 24095
           Summary: std.bitmanip.bitfields no longer works with bool enum
                    types
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: regression
          Priority: P1
         Component: phobos
          Assignee: nobody at puremagic.com
          Reporter: elpenguino+D at gmail.com

```
import std.bitmanip;

enum Bar : bool {
        a,
        b,
}

struct Foo {
        mixin(bitfields!(
                Bar, "bar", 1,
                ubyte, "", 7,
        ));
}
```
This compiled before DMD 2.103.0. Now it produces two errors: 'Error: operation
not allowed on `bool` `result <<= 7u`' and 'Error: operation not allowed on
`bool` `result >>>= 7u`'.

This regression appears to have been introduced by
https://github.com/dlang/phobos/pull/8663

--