[export_arm_cortexm] aidge_arm kernels need refactoring

We need to update existing aidge_arm kernel to use templates as much as possible and to make them use memory manager for handling memory wrapping.

Such kernels have been developed in N2D2: https://github.com/CEA-LIST/N2D2/blob/master/export/CPP_STM32/include/Network.hpp

We should use them as much as possible !

List of kernels to update:

• Sub: No broadcast no template
• Mul: Broadcast handling but no template
• Add: Broadcast handling but no template
• Div: Template but no handling of broadcasting
• MatMul: No template
• Softmax: No template
• Slice: No templates
• Sigmoid: remove aidge_sigmoid_flaot32.h
• Reshape: remove aidge_reshape_chw_float32.c
• ReLU: Add template
• BatchNorm: remove aidge_batchnorm2d_chw_float32.c add template