Added Fusion G3 NN library with kernels related to add, mul, quantize… (#6738)

* Added Fusion G3 NN library with kernels related to add, mul, quantize, dequantize, cat, layer norm, softmax to backends/cadence folder. Added operators to backends/cadence folder

* Updated name space of the operators by appending cadence

Signed-off-by: cmadhira@cadence.com <mckala@invecas.com>

* Added nnlib-FusionG3 submodule from FOSS-xtensa git space

Signed-off-by: cmadhira@cadence.com <mckala@invecas.com>

* Resolved Linter errors

Signed-off-by: cmadhira@cadence.com <mckala@invecas.com>

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Signed-off-by: cmadhira@cadence.com <mckala@invecas.com>
Co-authored-by: cmadhira@cadence.com <mckala@invecas.com>