sagemathgh-37260: extend `all_paths_iterator` and `all_simple_paths` to Graph
    
This answer a question from
https://ask.sagemath.org/question/75715/all_simple_paths-generates-
attributeerror-for-graphs/

We make methods `all_paths_iterator` and `all_simple_paths` work for
both `Graph` and `DiGraph`.

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### ⌛ Dependencies

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URL: sagemath#37260
Reported by: David Coudert
Reviewer(s): John H. Palmieri

sagemathgh-37260: extend `all_paths_iterator` and `all_simple_paths` to Graph
    
This answer a question from
https://ask.sagemath.org/question/75715/all_simple_paths-generates-
attributeerror-for-graphs/

We make methods `all_paths_iterator` and `all_simple_paths` work for
both `Graph` and `DiGraph`.

### 📝 Checklist

<!-- Put an `x` in all the boxes that apply. -->
<!-- If your change requires a documentation PR, please link it
appropriately -->
<!-- If you're unsure about any of these, don't hesitate to ask. We're
here to help! -->
<!-- Feel free to remove irrelevant items. -->

- [x] The title is concise, informative, and self-explanatory.
- [x] The description explains in detail what this PR is about.
- [x] I have linked a relevant issue or discussion.
- [x] I have created tests covering the changes.
- [x] I have updated the documentation accordingly.

### ⌛ Dependencies

<!-- List all open PRs that this PR logically depends on
- sagemath#12345: short description why this is a dependency
- sagemath#34567: ...
-->

<!-- If you're unsure about any of these, don't hesitate to ask. We're
here to help! -->
    
URL: sagemath#37260
Reported by: David Coudert
Reviewer(s): John H. Palmieri