insertParent to insert a new input node fail

Description

GraphView currently as the following functions:

• insertParent
• addChild

However, insertParent doesn't work to insert a new graph input because this method get the parent of the node to insert a parent to without checking if the parent already exists.

There is no addParent that would allow to easily insert a Parent to a graph.

There is no insertChild (related to aidge_quantization#91)

TODO

• Fix insertParent for graph input
• Add a function addParent
• Bind addParent function
• Add a function insertChild
• Bind insertChild function
• Add unittest
  • addParent
  • insertParent (add case node to insert to is graph input)
  • insertChild