[optim] Add general documentation on our algorithm defaults (#95391)
I added a section + table under Algorithms
https://docs-preview.pytorch.org/95391/optim.html?highlight=optim#module-torch.optim
<img width="725" alt="image" src="https://user-images.githubusercontent.com/31798555/221246256-99325a27-9016-407b-a9fe-404d61e41a82.png">
Pull Request resolved: https://github.com/pytorch/pytorch/pull/95391
Approved by: https://github.com/albanD
