enh: use enum_dispatch

[rbtcollins]

enum_dispatch could likely the box'd vtable code in the strategy implementation, leading to perhaps a 6x performance improvement, absent synchronisation issues. https://docs.rs/enum_dispatch/0.3.1/enum_dispatch/

[rbtcollins]

I've tested this, and at least for now, it has no performance benefit. I haven't tracked down why there is no benefit though.