polynomials/fix category

[mantepse]

We put polynomials (and friends) into the category of algebras with basis.

Dependencies: #38729

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[tscrim]

@nbruin @fchapoton @xcaruso cc-ing you in case you have some thoughts/comments about doing this.

[tscrim]

Since there are no comments, then positive review. (Something I've wanted to do for awhile, thank you!)

[xcaruso]

Thanks @tscrim for pointing this to me and sorry for not being reactive.
I actually do not have a strong opinion on this and I'm definitely happy with your positive review.

However, I should say that I'm quite confused with the dichotomy between the classes FreeModule and CombinatorialFreeModule. I think I understand that they support different kind of features: basically the former is more oriented towards linear algebra in finite dimension, while the former allows for infinite dimensional spaces, more abstract constructions (as tensor products, etc.) and custom names for elements in a basis. But, IMO, it's really a shame because we cannot having both at the same time.

Concretely, recently, I implemented Ore modules (see #38703) and was embarrassed by this. I finally chose to derive from FreeModule because I was interested in having submodules and quotients, two constructions which are more common in the class FreeModule. However, I was not entirely convinced.

Any thoughts about this? (Please answer in #38703 - and review this PR at the same time :-))