Meta-ticket: Run a more stable test suite on polyhedra

[gh-kliem]

We run more stable test for polyhedra using TestSuite.

Bug fixes:

• #29836: normaliz backend isn't ready for generators
• #29898: vertex facet graph for trivial polyhedra fails
• #29899: Two bugs with dilation
• #29904: Broken double description of hypercube
• #30328: Need to convert values before passing them to cdd
• #30330: cdd backend fails to initialize empty polyhedron from double description
• #31820: Fix pickling of normaliz representation objects

#29903: Run test suites for many examples. (All the following tickets depend on this one.)

Add new test methods:

• #29905: _test_basic_properties
• #29908is_combinatorially_equivalent,
• #29906: an_affine_basis,
• #29907: dilation,
• #29918: gale transform
• #29934: product
• #30293: lawrence construction
• #30292: pyramid
• #31821: Run the test suite of self.combinatorial_polyhedron()
• #31823: a_maximal_chain
• constructors and check such as pyramid -> is_pyramid

[gh-kliem]

Last 10 new commits:

​21f9d90	optional tag again
​bc2b7b7	Merge branch 'public/29836' of git://trac.sagemath.org/sage into public/29842
​b1d200b	add testsuite for dilation
​e41d698	fix universe from Hrep for cdd
​e055bc7	correctly detect the empty polyhedron
​444a178	Merge branch 'public/29899' of git://trac.sagemath.org/sage into public/29842
​7eba64d	trivial inequality
​8c4c083	Merge branch 'public/29899' of git://trac.sagemath.org/sage into public/29842
​067fb16	also fix it for initialization from Hrep and Vrep
​383b24e	Merge branch 'public/29899' of git://trac.sagemath.org/sage into public/29842

[git]

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

​790dfbc	fix trivial vertex facet graphs
​b8b8898	Merge branch 'public/29898' of git://trac.sagemath.org/sage into public/29842
​6ccbe4a	test is_combinatorially_isomorphic
​d7cca49	correct fix for 0-dimensional polyhedron
​4eea213	Merge branch 'public/29898' of git://trac.sagemath.org/sage into public/29842
​c42b966	test basic properties and test_an_affine_basis

[mkoeppe]

Sage development has entered the release candidate phase for 9.3. Setting a new milestone for this ticket based on a cursory review of ticket status, priority, and last modification date.