Succession diagram exposure

[jcrozum]

This PR reorganizes things a little bit for three reasons:

1. To make it so users can write balm.SuccessionDiagram.from_aeon(bn) instead of balm.SuccessionDiagram.SuccessionDiagram.from_aeon(bn).
2. Reduce ambiguity between the SuccessionDiagram class and module (the module is now called succession_diagram).
3. To make it easier to auto-generate the API docs later (the auto-doc can get confused when classes and modules share names, especially when we still have a not-quite-fully-resolved cyclic import problem).

[github-actions[bot]]

Coverage Report

File	Stmts	Miss	Cover	Missing
balm
control.py	123	14	89%	48, 57, 61, 67, 81, 90–106, 329, 332, 345
interaction_graph_utils.py	54	5	91%	6–8, 47, 165–166
motif_avoidant.py	152	2	99%	24, 120
petri_net_translation.py	148	11	93%	17–21, 57, 93, 206–207, 231–232, 241, 345
space_utils.py	129	4	97%	24–26, 251, 277
succession_diagram.py	247	12	95%	6, 163, 177, 185, 188, 205–206, 312, 439, 627, 665, 700
symbolic_utils.py	26	3	88%	10–12, 44
trappist_core.py	183	30	84%	10–14, 44, 46, 81, 128, 194, 196, 198, 226–229, 233–235, 255–261, 319, 321, 351, 391, 393, 424, 453
balm/_sd_algorithms
compute_attractor_seeds.py	30	1	97%	8
expand_attractor_seeds.py	51	5	90%	6, 42, 97–102
expand_bfs.py	28	1	96%	6
expand_dfs.py	30	1	97%	6
expand_minimal_spaces.py	37	2	95%	6, 31
expand_source_SCCs.py	164	6	96%	19–21, 91, 101, 143, 287
expand_to_target.py	31	3	90%	6, 38, 43
TOTAL	1474	100	93%

Tests	Skipped	Failures	Errors	Time
364	0 :zzz:	0 :x:	0 :fire:	49.565s :stopwatch:

[jcrozum]

Merging as per our discussion this morning.