gh-37451: combinat/free module tensor construction

    
This branch allows to change the base ring of a tensor product of free
modules:
```
            sage: F = CombinatorialFreeModule(ZZ, ['a','b','c']); F
            sage: T = F.tensor(F); T
            Free module generated by {'a', 'b', 'c'} over Integer Ring #
Free module generated by {'a', 'b', 'c'} over Integer Ring
            sage: T.change_ring(QQ)
            Free module generated by {'a', 'b', 'c'} over Rational Field
# Free module generated by {'a', 'b', 'c'} over Rational Field
```
    
URL: #37451
Reported by: Martin Rubey
Reviewer(s): Matthias Köppe, Travis Scrimshaw