use Parent in quotient rings too

[fchapoton]

instead of using the deprecated ParentWithGens

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[fchapoton]

strange:

sage: FiniteDimensionalAlgebra(k,[],assume_associative=True)
Finite-dimensional algebra of degree 0 over Finite Field of size 5

is not in Rings()

and also

sage: C = AlgebrasWithBasis(QQ).example()
sage: C in Rings()
True

sage: A=Algebras(QQ)
sage: A.super_categories()
[Category of rings,
 Category of associative algebras over Rational Field,
 Category of unital algebras over Rational Field]

[fchapoton]

and now we have that

sage: from sage.categories.magmatic_algebras import *
sage: cat1 = MagmaticAlgebras(GF(3)).FiniteDimensional().WithBasis()
sage: cat2 = Algebras(GF(3)).FiniteDimensional().WithBasis()
sage: cat1.Associative()
Category of finite dimensional associative algebras with basis over Finite Field of size 3
sage: cat1.Associative() is cat2
False
sage: cat2
Category of finite dimensional algebras with basis over Finite Field of size 3

and simplified problem is

sage: cat1 = MagmaticAlgebras(GF(3))
sage: cat2 = Algebras(GF(3))
sage: cat1.Associative() is cat2
False

seems to be a difference in Unital

sage: cat3=cat1.Associative()
sage: cat3
Category of associative algebras over Finite Field of size 3
sage: cat3.axioms()
frozenset({'AdditiveAssociative',
           'AdditiveCommutative',
           'AdditiveInverse',
           'AdditiveUnital',
           'Associative',
           'Distributive'})
sage: cat2.axioms()
frozenset({'AdditiveAssociative',
           'AdditiveCommutative',
           'AdditiveInverse',
           'AdditiveUnital',
           'Associative',
           'Distributive',
           'Unital'})
sage: cat3.Unital() is cat2
True

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[fchapoton]

I have now made a simple first step in #38375.