Docs / Quantization: refactor quantization documentation (#30942)

* refactor quant docs

* delete file

* rename to overview

* fix

* fix table

* fix

* add content

* fix library versions

* fix table

* fix table

* fix table

* fix table

* Apply suggestions from code review

Co-authored-by: Steven Liu <59462357+stevhliu@users.noreply.github.com>

* replace to quantization_config

* fix aqlm snippet

* add DLAI courses

* fix

* fix table

* fix bulet points

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Co-authored-by: Steven Liu <59462357+stevhliu@users.noreply.github.com>

docs/source/en/quantization/hqq.md

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+<!--Copyright 2024 The HuggingFace Team. All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
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+⚠️ Note that this file is in Markdown but contain specific syntax for our doc-builder (similar to MDX) that may not be
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+
+
+# HQQ 
+
+Half-Quadratic Quantization (HQQ) implements on-the-fly quantization via fast robust optimization. It doesn't require calibration data and can be used to quantize any model.  
+Please refer to the <a href="https://github.com/mobiusml/hqq/">official package</a> for more details.
+
+For installation, we recommend you use the following approach to get the latest version and build its corresponding CUDA kernels:
+```
+pip install hqq
+```
+
+To quantize a model, you need to create an [`HqqConfig`]. There are two ways of doing it:
+``` Python
+from transformers import AutoModelForCausalLM, AutoTokenizer, HqqConfig
+
+# Method 1: all linear layers will use the same quantization config
+quant_config  = HqqConfig(nbits=8, group_size=64, quant_zero=False, quant_scale=False, axis=0) #axis=0 is used by default
+```
+
+``` Python
+# Method 2: each linear layer with the same tag will use a dedicated quantization config
+q4_config = {'nbits':4, 'group_size':64, 'quant_zero':False, 'quant_scale':False}
+q3_config = {'nbits':3, 'group_size':32, 'quant_zero':False, 'quant_scale':False}
+quant_config  = HqqConfig(dynamic_config={
+  'self_attn.q_proj':q4_config,
+  'self_attn.k_proj':q4_config,
+  'self_attn.v_proj':q4_config,
+  'self_attn.o_proj':q4_config,
+
+  'mlp.gate_proj':q3_config,
+  'mlp.up_proj'  :q3_config,
+  'mlp.down_proj':q3_config,
+})
+```
+
+The second approach is especially interesting for quantizing Mixture-of-Experts (MoEs) because the experts are less affected by lower quantization settings.
+
+
+Then you simply quantize the model as follows
+``` Python
+model = transformers.AutoModelForCausalLM.from_pretrained(
+    model_id, 
+    torch_dtype=torch.float16, 
+    device_map="cuda", 
+    quantization_config=quant_config
+)
+```
+
+## Optimized Runtime
+
+HQQ supports various backends, including pure Pytorch and custom dequantization CUDA kernels. These backends are suitable for older gpus and peft/QLoRA training.
+For faster inference, HQQ supports 4-bit fused kernels (TorchAO and Marlin), reaching up to 200 tokens/sec on a single 4090.
+For more details on how to use the backends, please refer to https://github.com/mobiusml/hqq/?tab=readme-ov-file#backend