Field from anonymous bitfield in other unit not resolved

[bbannier]

If a bitfield field was lifted into its unit we do not find it when operating from a different unit.

module foo;

type X = unit {
    : bitfield(8) {
        a: 0..7;
    };
};

type Y = unit(x: X) {
    on %init { print x.a; }
};

$ spicyc -dj foo.spicy
[error] foo.spicy:10:22: type does not have field 'a'
[error] spicyc: aborting after errors

[bbannier]

@rsmmr I added this to the bitfield tracking ticket so we can make sure to get to it before zeek-6.1.