docs: add tutorial for score-based methods that covers all new features

[janfb]

the current tutorial for score-based SBI methods covers just the basic API: https://sbi-dev.github.io/sbi/dev/tutorials/16_implemented_methods/

Recently, we have fixed some bugs and implemented a bunch of improvements and new features for score-based methods.

These functionalities should be covered in a new dedicated tutorial, e.g., covering the different sampling options, convergence properties and extra features like i.i.d. sampling etc.

see #1370 #1381