Fix aerodynamic_analysis gnuplot not terminating issue

Description

Previously on linux, aerodynamic_analysis terminated only with the help of pkill (killing a gnuplot instance, which was not closed). This is now solved without pkill.

• Instead of using the function to generate the plots, each plot is directly created within the routine.

Testing Instructions

1. Build on unix
2. execute and expect aerodynamic_analysis closing

Developer Checklist

• Code has been tested locally and/or in pipeline.
• (if applicable) documentation updated.
• (if applicable) impact of new dependencies reviewed and included in project.
• Merge conflicts resolved with the target branch.