Shift<T> ergonomics

[oscbyspro]

The current ergonomics of Shift<T> is terrible. I just haven't gotten around to fixing it yet.

Shift<T.Magnitude>(unchecked: Count(unchecked: index)) // ugh!

[oscbyspro]

I'll add a Shift<T>.one convenience because shifting by 1 is common:

integer.up  (Shift.one)
integer.down(Shift.one)

Note that the minimum binary integer size is 8 bits, so it is always valid. It also reads well.

[oscbyspro]

Writing Shift<T.Magnitude> is a bit cumbersome, so I might consider a T.Shift alias:

extension BinaryInteger { public typealias Shift = CoreKit.Shift<Magnitude> }