test subNormedZmodType

[affeldt-aist]

Motivation for this change

We are trying to define SubNormedZmodule like the Sub structures in MathComp
(we are doing this in MathComp-Analysis to test it because ultimately we want SubNormedModule
but we are not there yet)

Adding SubNormedZmodule just after SubSemiNormedZmodule seems to do what we want
in MathComp (see this branch https://github.com/affeldt-aist/math-comp/commits/numdomain_20240403/)
but in MathComp-Analysis it generates the following error message:

Structure pseudometric_normed_Zmodule_SubSemiNormedZmodule
contains the same mixins as SubNormedZmodule

when I tried to define SubNormedZmodule and in a context where
pseudometric_normed_Zmodule_SubSemiNormedZmodule does not exist yet

@mkerjean @CohenCyril

Checklist

• added corresponding entries in CHANGELOG_UNRELEASED.md

• added corresponding documentation in the headers

Reference: How to document

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