🎉 Use the bitvec crate

[LinusU]

This removes a lot of unsafe code, but currently comes at quite a heavy performance cost unfortunately:

Like a Rolling Stone    time:   [1.8420 s 1.8436 s 1.8456 s]                                    
                        change: [+79.128% +79.425% +79.742%] (p = 0.00 < 0.05)
                        Performance has regressed.