Remove doctests in `combinatorial_polyhedron/conversions.pyx` that depend on implementation details

[kliem]

We remove doctests that depend on implementation of the bitsets and exchange those by tests that check that conversion back and forth works correctly.

In addition we remove the deprecation warnings from #28608 in this file. Those functions aren't meant for public use anyway and the old names were exposed for a rather short period (sage 8.9 and sage 9.0).

CC: @jplab @LaisRast @tscrim

Component: geometry

Reviewer: Travis Scrimshaw

Issue created by migration from https://trac.sagemath.org/ticket/30571

[kliem]

Branch: u/gh-kliem/prepare_conversions_for_face_structure

[kliem]

Last 10 new commits:

fc8124a	fix mistake
3e30d07	add doctest functions for combinatorial_polyhedron/conversions.pyx
41ed120	simplify doctest in list_of_faces
1529987	simplify doctessts in polyhedron face lattice
7b134d5	Merge branch 'u/gh-kliem/simplify_conversion_tests' of git://trac.sagemath.org/sage into u/gh-kliem/no_more_basic_access_2
072e200	temporary commit
cba37e8	temporary commit
0b41c77	remove basic acces to bitsets
7a32286	removed deprecated functions
af27e02	remove doctests that rely on implementation details

[kliem]

Commit: af27e02

[tscrim]

comment:2

LGTM.

[tscrim]

Reviewer: Travis Scrimshaw

[kliem]

comment:3

Thank you.

[kliem]

comment:4

With #30528 gone, it's hard to make this work on it's own.