Update OOP advanced notebook (#302)

* Add recap, one quiz per section, reorg exercises, update toc
* Fix "Banking system"
* Finish updating exercises
* Fixes after review
* A few more details on class decorators
* Few typos
* Link to `attrs`
* Removed redundant quiz
* Test, exercise 1: fix return type hint

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Co-authored-by: Edoardo Baldi <edoardob90@gmail.com>
Co-authored-by: Aliaksandr Yakutovich <yakutovicha@gmail.com>

Author: 3 people