Adding MulCompensation Nodes to the PTQ pipeline

Compared to this MR: !22 (merged)

The files PTQMetaOps.hpp and PTQMetaOps.cpp have been moved to:

• include/aidge/operator/PTQMetaOps.hpp
• src/operator/PTQMetaOps.cpp.

Pybind bindings for the following meta-operators:

• Quantizer
• Scaling
• MulCompensation
• Utility functions related to these meta-operators.

Introducing a new meta-operator, MulCompensation. This operator encapsulate a single Mul operation (similar to the Scaling meta-operator) and serve as a clear tag for compensation nodes.

See Issue: #50 (closed)