[core] Add better handling of gnu_plot in optimized memory manager

• Add option to plot mem info or not
  • Via an optional argument in the function
  • Document the new argument in the docstring
• Catch error if gnu_plot is not installed

The code to modify is the following: https://gitlab.eclipse.org/eclipse/aidge/aidge_core/-/blob/dev/aidge_core/mem_info.py?ref_type=heads#L77-86