Refactor lava messaging and implement remaining PyPorts

[mgkwill]

Implement:

• PyInPortVectorSparse
• PyInPortScalarDense
• PyInPortScalarSparse
• PyOutPortVectorSparse
• PyOutPortScalarDense
• PyOutPortScalarSparse

Retrofit to work with other input types/shapes:

• PyInPortVectorDense

https://github.com/lava-nc/lava/blob/9d80ea15af495b87df7f4b63e83531bdaf7d41f9/lava/magma/core/model/py/ports.py#L53-L75

Ensure that ports process data correctly when receiving from the matrix:

	Vector	Vector	Scalar	Scalar
-----------	-Receive- Dense	-Receive- Sparse	-Receive- Dense	-Receive- Sparse
Vec -Send- Dense	-------	-------	-------	-------
Vec -Send- Sparse	-------	-------	-------	-------
Sca -Send- Dense	-------	-------	-------	-------
Sca -Send- Sparse	-------	-------	-------	-------