gh-35896: deal with bad chosen representations of k-regular sequences
    
### 📚 Description

It deals with the situation when mu[0]*right != right in k-regular
sequences.

Fixes #21343. This PR is created from the branch/code that has been on
the corresponding trac ticket + merging in a current SageMath version.

See also meta issue #21202.

### 📝 Checklist

- [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

- #21204: guessing k-regular sequences from the first few values

No formal dependencies, but there are trivial merge conflicts---in both
branches, methods are inserted at the same position in the code---
between:
- #21343: deal with mu[0]*right != right in k-regular sequences
- #35894: Regular sequences: implement convolution / ring structure
    
URL: #35896
Reported by: Daniel Krenn
Reviewer(s): cheuberg, Daniel Krenn

Author: Release Manager

src/doc/en/reference/references/index.rst

@@ -3102,8 +3102,9 @@ REFERENCES:
              with tunable clustering*, Phys. Rev. E (2002). vol 65, no 2, 026107.
              :doi:`10.1103/PhysRevE.65.026107`.
 
-.. [HKL2021] Clemens Heuberger, Daniel Krenn, Gabriel F. Lipnik, "Asymptotic
-             Analysis of `q`-Recursive Sequences", :arxiv:`2105.04334`, 2021.
+.. [HKL2022] Clemens Heuberger, Daniel Krenn, Gabriel F. Lipnik, "Asymptotic
+             Analysis of `q`-Recursive Sequences". Algorithmica **84** (2022),
+             2480–2532. :doi:`10.1007/s00453-022-00950-y`.
 
 .. [HKOTY1999] \G. Hatayama, A. Kuniba, M. Okado, T. Tagaki, and Y. Yamada,
                *Remarks on fermionic formula*. Contemp. Math., **248** (1999).