Intgerate Intel® Extension for Transformers weight-only quantization into Lightning Fabric API

[yuwenzho]

What does this PR do?

We are the team working on the development of Intel® Extension for Transformers. We would like to discuss the quantize feature in relation to our projects.

Allow us to provide an introduction to both projects firstly:

• Intel® Extension for Transformers (ITREX) is an innovative toolkit to accelerate Transformer-based models on Intel platforms, in particular effective on 4th Intel Xeon Scalable processor Sapphire Rapids (codenamed Sapphire Rapids).

We would like to integrate ITREX into the PyTorch Lightning Fabric API. This integration could involve INT8/INT4/FP4/NF4 weight-only quantization feature.

Here is a simple use case:

from lightning.fabric.plugins import ITREXPrecision

precision = ITREXPrecision(mode="int8") # mode: Literal["int8", "int4_fullrange", "int4_clip", "nf4", "fp4_e2m1"]
fabric = Fabric(plugins=precision)
model = MyModel()
model = fabric.setup(model)

For more details of ITREX 4-bit, please refer to the medium blog of Intel-Optimized Llama.CPP

For #18770

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📚 Documentation preview 📚: https://pytorch-lightning--19125.org.readthedocs.build/en/19125/

[codecov]

Codecov Report

Merging #19125 (93f1de3) into master (b5d4ee5) will decrease coverage by 30%.
Report is 149 commits behind head on master.
The diff coverage is 48%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #19125      +/-   ##
==========================================
- Coverage      83%      54%     -30%     
==========================================
  Files         445      441       -4     
  Lines       37289    37212      -77     
==========================================
- Hits        31107    19994   -11113     
- Misses       6182    17218   +11036     

[yuwenzho]

Please review this PR.

[gitguardian]

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