Improve syntax of process_id property in the Desktop() class

[Devin-Crawford]

Description of the current limitations

The property name aedt_process_id should be renamed to process_id. The prefix aedt is redundant and unnecessary since the process_id property is associated with the Desktop() class.

Code sample expected

Add aedt_process_id with a
@property wrapper and deprecation warning. Replace all instances of the property with process_id.

Useful links and references

https://github.com/ansys/pyaedt/blob/main/src/ansys/aedt/core/desktop.py