Remove using namespace std from header files

[TimmRuppert]

Reference to a related issue in the repository

Fixes https://github.com/OpenSimulationInterface/osi-sensor-model-packaging/issues/114

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Remove using namespace std and add full qualifier where needed

Check the checklist

• [x] I have performed a self-review of my own code.
• [ ] I have made corresponding changes to the documentation for osi-sensor-model-packaging.
• [x] My changes generate no new warnings.
• [ ] I have added tests that prove my fix is effective or that my feature works.
• [x] New and existing unit tests / Github Actions pass locally with my changes.