Fix add wishart wishartfast prod

[Nimrais]

This PR addresses two issues:

#192: Missing product definition between Wishart and WishartFast
#216: ProductOf{InverseWishart, InverseWishartFast} not dispatched correctly

Added product rules for:

1. Wishart × WishartFast
2. InverseWishart × InverseWishartFast

The implementation converts the standard distribution to its "Fast" variant before computing the product, since *Fast variants are optimized versions of the same distributions used for messages.

Note: The product between two standard Wishart distributions is postponed until we have a specific model requiring this functionality.

[wouterwln]

Looks like you beat me to it. Will this not break if Wishart or InverseWishart is on the right side instead of left? And can you add tests for InverseWishart too?

[Nimrais]

Ah hoped that you already have tests, yeah I will do.

[Nimrais]

Will this not break if Wishart or InverseWishart is on the right side instead of left?

not it does not - I have test for this. In bayes base we check if there is a rule if we will swap the arguments.

[wouterwln]

Perfect. Poke me if you're done, I will review and merge.