webnn: Support int4 dequantization and per-channel quantization

1, Emulate the quantize operation whose calculation follows the
   expression `clamp(tfl.round(input / scale) + zeroPoint, 0, 255)`.
2, Support pre-channel quantization and dequantization
3, Support int4 dequantization, but quantization operation doesn't
   support int4 for tfl.quantize operator and it can't be emulated
   because the cast operation also doesn't support int4.

Bug: 375614290, 376722724
Change-Id: Iccbf69d8426e5729b35455357c99f00effaa21e2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6015965
Commit-Queue: Junwei Fu <junwei.fu@intel.com>
Reviewed-by: ningxin hu <ningxin.hu@intel.com>
Reviewed-by: Reilly Grant <reillyg@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1385963}