sage.features: Move classes from __init__ to separate modules

[mkoeppe]

In the long term we should get rid of __init__.py so that this package can become a namespace package (see #28925)

CC: @tobiasdiez @saraedum @kiwifb @dimpase @tscrim @seblabbe

Component: refactoring

Work Issues: drop 2nd commit, rebase on #32925

Author: Matthias Koeppe

Branch/Commit: u/mkoeppe/sage_features__move_classes_from___init___to_separate_modules @ bad5d50

Issue created by migration from https://trac.sagemath.org/ticket/31293

[mkoeppe]

Branch: u/mkoeppe/sage_features__move_classes_from___init___to_separate_modules

[sagetrac-git]

Commit: bad5d50

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

bad5d50

sage.features: Split out module feature

[mkoeppe]

comment:4

Setting new milestone based on a cursory review of ticket status, priority, and last modification date.

[mkoeppe]

Author: Matthias Koeppe

[kiwifb]

comment:6

This is just code re-org, you are just shuffling things around cut and paste style. Looks OK to me, but I'd like someone else to double check that I am not missing anything.

[mkoeppe]

Work Issues: drop 2nd commit, rebase on #32925