[SofaHelper] Factory key type can be other than std::string

[alxbilger]

Factories were used only with std::string as a key. That is why it was not noticeable that factories were not compatible with other types than std::string as the key.
The limitations come from:

• logFactoryRegister assumed Key is a string. It is now a template function.
• Creator inherits from Key and instances was used such as it was a string. Now, Creator no longer inherits from Key but just stores the key as a class member.

A unit test is added for enum type as a key.

Small downside: std::string& getFactoryLog() is now available outside the translation unit.

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• it builds with SUCCESS for all platforms on the CI.
• it does not generate new warnings.
• it does not generate new unit test failures.
• it does not generate new scene test failures.
• it does not break API compatibility.
• it is more than 1 week old (or has fast-merge label).

[alxbilger]

[ci-build][with-all-tests]

[fredroy]

Lots of weird stuff happening with those *_API (dllimport/dllexport) thingies 🥴
TIL I learnt that you cannot put it after the type if it is a reference (I suppose the & bothers the compilation)
Seems better to put it always before the type.