sagemathgh-37831: FreeModuleHomset: Create subclass `FreeModuleEnds…

…et`, add element methods for invariants `det`, `charpoly`, `fcp`, etc.

    
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We create
- a parent subclass `FreeModuleEndset` (of `FreeModuleHomset`)
- an element subclass `FiniteRankFreeModuleEndomorphism` (of
`FiniteRankFreeModuleMorphism`)

for the purpose of providing specific methods of endomorphisms, namely
the endomorphism invariants `det`, `trace`, `charpoly`, etc.

This is parallel to what is done
- for ModulesWithBasis in sagemath#37731
- in sagemath#37826

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preview.

### ⌛ Dependencies

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URL: sagemath#37831
Reported by: Matthias Köppe
Reviewer(s): Eric Gourgoulhon, Travis Scrimshaw