some code cleanup in WeierstrassIsomorphism

[yyyyx4]

This is mainly to reduce the amount of code duplication in sage.schemes.elliptic_curves.weierstrass_morphism.isomorphism by turning it into a generator, plus generic style tweaks.

I consider the second commit (renaming isomorphisms() to _isomorphisms()) optional: The function has been marked as "not intended for users" forever, so I figured we might as well just hide it. Note that this does not affect the EllipticCurve_generic.isomorphisms() method in any way.

CC: @JohnCremona

Component: elliptic curves

Author: Lorenz Panny

Branch/Commit: 99a6e3b

Reviewer: John Cremona

Issue created by migration from https://trac.sagemath.org/ticket/34722

[sagetrac-git]

Changed commit from 6072f48 to fd812d2

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. This was a forced push. New commits:

5b840c6	some code cleanup around WeierstrassIsomorphism
fd812d2	hide internal function

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. This was a forced push. New commits:

cf49d57	some code cleanup around WeierstrassIsomorphism
99a6e3b	hide internal function

[sagetrac-git]

Changed commit from fd812d2 to 99a6e3b

[yyyyx4]

Reviewer: John Cremona

[yyyyx4]

comment:4

Setting to positive review per #34728 comment:5 and #34728 comment:7.

[vbraun]

Changed branch from public/some_WeierstrassIsomorphism_cleanup to 99a6e3b