Cheaper test variants for Github Actions

[mscho527]

Try to reduce time for expensive tests
Use exxdiv=None before #61
Ask pytest to always log expensive tests and time breakdown

7min / tests --> 5.5 min on github actions; save cpu hrs, save the planet :)

[mscho527]

============================== slowest durations ===============================
69.93s call     tests/chempot_molBE_test.py::TestBE_restricted::test_octane_sto3g_ben
24.32s call     tests/molbe_octane_test.py::test_octane_molbe
22.54s call     tests/molbe_octane_get_rdms_test.py::test_rdm
20.81s call     tests/kbe_polyacetylene_test.py::test_polyacetylene
18.93s call     tests/molbe_octane_test.py::test_cubegen
18.18s call     tests/fragmentation_test.py::TestBE_Fragmentation::test_graphgen_autogen_octane_be2

The top one takes a while because it is doing both BE2 and BE3. We could change BE3 for octane to BE3/MP2, but perhaps on a different PR? I think this change could be potentially somewhat contentious.

[mcocdawc]

just a short question about the pytest call. Otherwise looks good to me

[mcocdawc]

cool cool nice nice