add parameter immutable to cosetGraph

[dcoudert]

Following discussions in #39177, we add the option to return immutable graphs to method cosetGraph of class AbstractLinearCode.
On the way, we add parameter immutable to method sage.graphs.generators.families.HammingGraph and to some methods using cosetGraph in src/sage/graphs/generators/distance_regular.pyx.

📝 Checklist

• The title is concise and informative.
• The description explains in detail what this PR is about.
• I have linked a relevant issue or discussion.
• I have created tests covering the changes.
• I have updated the documentation and checked the documentation preview.

⌛ Dependencies

[dcoudert]

We also observe a speed up in distance_3_doubly_truncated_Golay_code_graph

Before:

sage: %time G = graphs.distance_3_doubly_truncated_Golay_code_graph()
CPU times: user 1.54 s, sys: 5.65 ms, total: 1.55 s
Wall time: 1.55 s

After

sage: %time graphs.distance_3_doubly_truncated_Golay_code_graph(immutable=True).is_immutable()
CPU times: user 1.04 s, sys: 3.84 ms, total: 1.04 s
Wall time: 1.04 s
True
sage: %time graphs.distance_3_doubly_truncated_Golay_code_graph(immutable=False).is_immutable()
CPU times: user 1.01 s, sys: 4.11 ms, total: 1.02 s
Wall time: 1.02 s
False

[github-actions]

Documentation preview for this PR (built with commit 88eee87; changes) is ready! 🎉
This preview will update shortly after each push to this PR.

[fchapoton]

ok, good.