Installing python modules correctly [20800]

[richiware]

Description

This PR improves the installation of the python module, especially on windows.

• Instead of install site-packages/fastdds.py, it install site-packages/fastdds/__init__.py. It's more python style.
• The user doesn't have to import the C++ DLL file himself (win32api.LoadLibrary()). It is the python module who did it now.

Code generated with this PR:

• Installing python modules correctly [21071] Fast-DDS-Gen#348

Contributor Checklist

• Commit messages follow the project guidelines.
• N/A Tests that thoroughly check the new feature have been added/Regression tests checking the bug and its fix have been added; the added tests pass locally
• Changes are API compatible.
• N/A Applicable backports have been included in the description.

Reviewer Checklist

• The PR has a milestone assigned.
• The title and description correctly express the PR's purpose.
• Check contributor checklist is correct.
• Check CI results: changes do not issue any warning.
• Check CI results: failing tests are unrelated with the changes.

[EduPonz]

LGTM with rebase and CI