The existing implementation uses Python to launch a set of Rust-written
binaries. Unfortunately, this is currently broken; it seems that some
updates meant it no longer compiles.
There is also a problem that support for more float types (`f16`,
`f128`) would be difficult to add since this is very specialized to
`f32` and `f64`.
Because of these sortcomings, migrate to a version written in Rust. This
version should be significantly faster; test generators can execute in
parallel, and test cases are chunked and parallelized. This should also
resolve the preexisting "... the worker processes are leaked and stick
around forever" comment.
This change also introduces genericism over float types and properties,
meaning it will be much easier to extend support to newly added types.
`num::BigRational` is used in place of Python's fractions for
infinite-precision calculations.
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