Consider bitmask alternatives

[arcnmx]

The bitmask/enum_iterator utils really don't belong in this repo. Ideally a crate like enumflags would serve their purpose, but at the time it wasn't generic enough to work with backing data structures that aren't numeric primitive types. Perhaps that's changed now, or can be avoided?

If not, consider cleaning these types up and creating a new bitflags crate now that const generics and GATs might help make them more ergonomic.