[Inductor] Add Int8 data type into Inductor CPP backend vectorized code generation (#119179)
**Summary**
Part 1 of fixing https://github.com/pytorch/pytorch/issues/119141 which needs vectorized code generation of per channel quant and int8 data type.
In the current implementation for quantization, the vectorized code generation only supports the `uint8` data type. In this PR, we introduce support for the `int8` data type within the vectorized code generation.
**TestPlan**
```
python -u -m pytest -s -v test_cpu_repro.py -k test_decomposed_dequant_relu_quant_int8
python -u -m pytest -s -v test_cpu_repro.py -k test_dequant_quant_lowering_int8
python -u -m pytest -s -v test_cpu_repro.py -k test_dequant_maxpool2d_lowering_int8
python -u -m pytest -s -v test_cpu_repro.py -k test_tile2d_load_decomposed_dequant_add_relu_quant_int8
python -u -m pytest -s -v test_cpu_repro.py -k test_per_tensor_fake_quant_int8
python -u -m pytest -s -v test_cpu_repro.py -k test_non_contiguous_load_buf_quant_int8
python -u -m pytest -s -v test_cpu_repro.py -k test_tile2d_store_channel_shuffle_cl_quant_output_int8
python -u -m pytest -s -v test_cpu_repro.py -k test_dequant_relu_quant_dequant_relu_quant_lowering_int8
```
Co-authored-by: Jiong Gong <jiong.gong@intel.com>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/119179
Approved by: https://github.com/peterbell10, https://github.com/jgong5, https://github.com/jansel
