gh-36325: Refactor Drinfeld modules subclasses
    
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The goal of this PR is to refactor the Drinfeld modules subclasses. In
particular, we rename `FiniteDrinfeldModule` into
`DrinfeldModule_finite` and we create a new class named
`DrinfeldModule_charzero`.  The second class denotes a Drinfeld module
which is defined over a ring of $\mathbb{F}_q[T]$-characteristic zero.
More conceptually, we propose the following structure:
```
    DrinfeldModule
        - DrinfeldModule_finite
        - DrinfeldModule_charzero
```
The user will only have to interact with the metaclass `DrinfeldModule`.

This refactorisation ensures that the exponential, the logarithm and the
Goss polynomials methods always works as these are not defined in the
finite case (and thus removes the required check).

In the near future, we plan to implement
`DrinfeldModule_charzero_rank_one` as a subclass of
`DrinfeldModule_charzero` and implement their associated $A$-lattice.

CC: @kryzar @xcaruso @ymusleh

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URL: #36325
Reported by: David Ayotte
Reviewer(s): David Ayotte, Xavier Caruso

Author: Release Manager

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

@@ -12,6 +12,7 @@ Drinfeld modules
    :maxdepth: 2
 
    sage/rings/function_field/drinfeld_modules/drinfeld_module
+   sage/rings/function_field/drinfeld_modules/charzero_drinfeld_module
    sage/rings/function_field/drinfeld_modules/finite_drinfeld_module
 
 Morphisms and isogenies