Create a target for each python version

[alkino]

So this PR create targets Python::Python3.8, Python::Python3.9, ... It stores them in a list NRN_PYTHON_TARGETS.

More over there is the default python that is a target Python::Python aliased to the right target.

It creates too targets Python::Interpreter3.8, ...

[azure-pipelines[bot]]

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Quality Gate passed

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