Integrate a native GIN algorithm with constraint algorithms

[robertness]

Is your feature request related to a problem? Please describe.
Implement GIN as a native algorithm.

Describe the solution you'd like
We have a wrapper around causal-learn for the GIN algorithm. The GIN algorithm uses kernel-based conditional independence tests. So do we. In the very least we can leverage our KCI test and other CI tests. In my view, GIN is a constraint-based algorithm (that learns latents) and should be with other constraint-based algorithms. @adam2392

A native implementation would help us apply constraints as well.

Describe alternatives you've considered
Could stay in a separate directory for causal rep related algorithms.