fix the behavior for immutable graphs in methods related to isomorphisms in sage/graphs/generic_graph.py

[dcoudert]

Following #39280 and discussions in #39177, we add parameter immutable to methods related to graph isomorphisms in sage/graphs/generic_graph.py and bliss.pyx:

• canonical_form
• automorphism_group
• is_isomorphic
• graph_isom_equivalent_non_edge_labeled_graph
• and also cayley_graph

We also fix the behavior of method canonical_label in BipartiteGraph.

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