Arm Ethos U55/U85 Int16 Ops Support

[Ninja91]

Top level task to add support for INT16 ops support.
To begin with, we focus on:

• QuantizeNode
• DequantizeNode
• ReshapeNode
• LSTM
  • FCNode
  • MulNode
  • AddNode
  • RequantizeNode
  • SigmoidNode
  • TanhNode
  • ReshapeNode
  • SliceNode
  • StackNode
• LayerNorm
  • ReduceMeanNode
  • RsqrtNode
  • ReciprocalNode

Individual ops task will be added as sub tasks

cc @digantdesai @freddan80 @per @zingo @oscarandersson8218

[Ninja91]

@per @3l1 @digantdesai This is the master task for adding support for Int16 ops and also lists P0 ops to support,