Update base for Update on "Arm backend: Add INT16 support to rescale operation"

Add INT16 support for RequantizeNode rescale operations in ExecutorTorch ARM backend.

This follows the pattern established for linear, mul, sigmoid, tanh, slice, view/transpose, cat, and FCNode operations, extending int16 support to RequantizeNode rescale operations.

Changes:
- Add INT16 dtype validation support in op_rescale.py
- Enable rescale operations for 16A8W quantization configuration

The 16A8W configuration uses 16-bit activations with 8-bit weights, enabling higher precision for activations while maintaining weight efficiency. RequantizeNode rescale operations are essential for proper quantization scaling in the 16A8W pipeline.

Differential Revision: [D80513725](https://our.internmc.facebook.com/intern/diff/D80513725/)

cc digantdesai freddan80 per zingo oscarandersson8218

[ghstack-poisoned]

Author: Ninja91