Consider removing const generics

[sragss]

Surge makes extensive use of const generics to allow statically sized arrays throughout rather than Vectors or Slices.

In order to use this pattern through our generic SubtableStrategy traits we require the use of feature(generic_const_exprs) which is highly unstable. Beyond the instability, we have strange artifacts on many of our impls, such as [(); S::NUM_SUBTABLES]: Sized. These tell the compiler that the const generic expression is bounded.

It's likely that the overhead of using Slices and len asserts everywhere is minimal enough to be irrelevant. It's worth considering whether the benefit is worth the downside.