DOC: Consolidate pages under /docs/getting_started

[mroeschke]

Another piece of feedback from the CZI EOSS kickoff meeting that @WillAyd and I attended:

In https://pandas.io/docs/getting_started/index.html, we link to the following pages in the left side:

We got feedback to:

1. Have a dedicated link to the pandas cheat sheet: https://github.com/pandas-dev/pandas/blob/master/doc/cheatsheet/Pandas_Cheat_Sheet.pdf
2. Consolidate Getting started tutorials, Tutorials, and 10 minutes to pandas (which is linked already in Tutorials) into a singular Tutorials page

[WillAyd]

Also from the home page clicking “Getting Started” in the nav bar will take you to a different target than clicking the “Getting Started” link that shows under the “Getting Started” bullet points on the left hand side of the home page

[WillAyd]

Sorry noticed you have above comment of mine already addressed in #32307

[jorisvandenbossche]

The current "Tutorials" are mostly (outdated) external tutorials, so I am not sure I would combine it into one of the other pages. Another option could also to rename it to eg "External tutorials" or something like that to make the name clearer.
What was the concrete idea? To put it as one of the additional pages under "Tutorials" or to put it on a tutorials/index.rst landing page?

I am not fully sure what best to do with the "10min to pandas", personally.

Good idea about adding a more visible link to the cheatsheet.

BTW, IMO we should also move "Essential basic functionality" and "Intro to data structures" back to the user guide (since those are not written as introductory getting started material)