Generalize core primitives to abstract number type

[sorki]

We can turn circle :: ℝ -> SymbolicObj2 into e.g. circle :: Num a => a -> SymbolicObj2 a.

That would allow us to use different numerical types instead of being fixed on Doubles. Some fun examples include

• discrete type like Integer
• arbitrarily precise CReal from https://hackage.haskell.org/package/exact-real
• symbolic Sym from https://hackage.haskell.org/package/numbers-3000.2.0.2/docs/Data-Number-Symbolic.html
• ℝ from promote ℝ to an instance of a typeclass #225
• types with dimensions (units or dimensional)

It would also open a lot of doors to other backends like accelerate or GLSL, where symbolic objects could be represented as, well.. symbolic functions.

Also an analytical simplification step could be implemented before actual discretization and evaluation which could drastically improve performance for some cases.