Consolidate optimizer readme into datafusion user guide

[alamb]

Is your feature request related to a problem or challenge?

The DataFusion optimizer has a great readme:

https://github.com/apache/datafusion/tree/main/datafusion/optimizer#readme

However, I don't think it is as discoverable as the Library guide on the docs site: https://datafusion.apache.org/library-user-guide/index.html

Describe the solution you'd like

Consolidate the content from https://github.com/apache/datafusion/tree/main/datafusion/optimizer#readme into https://datafusion.apache.org/library-user-guide/index.html

I think we could start with simply moving the content and leaving a link in the readme and then update the content in subsquent PRs

Describe alternatives you've considered

No response

Additional context

No response

[devesh-2002]

May I take this issue?

[alamb]

Thank you @devesh-2002 -- that would be super helpful