Variability: Ports of components with behavioral specification shall never be optional

Optional ports can lead to problems in behavioral specifications, such as code specifications or state automata. Hence, optional ports should not be added to such components, as long as the analysis in #4495 is not yet implemented.

Since optional ports might still be correct (e.g. the port might not be used or the port is only used on transitions with the same presence condition) only a warning shall be generated.

Test instructions:

• Import this AF3 project: AF3-Project.af3_23
• Observe: There is a warning for a port.
• Remove the presence condition for this port.
• Save the model
• Observe: The warning is gone.
• Try to add a presence condition to the port again.
• Observe: The text fiel ist disabled