Refresh "Quantization Overview" docs page

[andrewor14]

https://docs.pytorch.org/ao/main/quantization.html

Our Quantization Overview docs page is a bit outdated and too developer focused. We should structure it around:

• Two main quantization APIs, quantize_ and PT2E ones
• Different quantization features supported, example user code snippets, link to different doc pages
• Move all developer concepts (e.g. AQT, layout, quant primitives) to a separate page
• Delete static quant and serialization sections. These have their own tutorials
• Refresh dtypes supported (still mentions adding torch.uint2), add newer mx dtypes
• Replace ascii art with real image

[jerryzh168]

partially addressed by #2723

ascii art is for easy modification btw, so I think it's fine to keep it