vmlogic: split up into two

The split boundary has been chosen to be what's necessary to compute a
VMOutcome, which now in turn allows us to load a contract without
constructing a VMLogic, or contract memory quite yet.

This might very well resolve issues I've been working through by
attempting to remove lifetimes and such from `VMLogic`...? As previous
changes this makes quite some sense in isolation regardless of the
ongoing projects. While I imagine there are more lines, they will mostly
be due to the fact that in many places the previous code now needs to go
through an additional field projection to get to types it needs to
operate.