gh-37955: `Graph.{[weighted_]adjacency_matrix,kirchhoff_matrix}`: Support constructing `End(CombinatorialFreeModule)` elements
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This is a follow-up after
- #37692
... to cover a few more methods. The methods can now create
endomorphisms of free modules whose bases are indexed by the vertices.
To help with this, we make the `matrix` constructor a bit more flexible.
This is also preparation for making the spectral graph theory methods
ready for `CombinatorialFreeModule`:
- #37943
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### :hourglass: Dependencies
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URL: https://github.com/sagemath/sage/pull/37955
Reported by: Matthias Köppe
Reviewer(s): David Coudert, Matthias Köppe
