Doc/generalize tutorials

[musslick]

Description

I added general context for the main tutorials introducing an experimentalist and theorist.

Type of change

• docs: Documentation only changes

Remarks (Optional)

• @younesStrittmatter We would want to add, in a separate PR, a similar introduction to a simple closed-loop tutorial involving fire base.
• @benwandrew We would want to add, in a separate PR< a similar introduction to a synthetic closed-loop tutorial.

[benwandrew]

added a couple language edits in the theorist notebook and made a note about new experimentalist image, but otherwise this looks great!

[benwandrew]

just a note: i think with the new image for the experimentalist (https://github.com/AutoResearch/autora/blob/doc/exp-module/docs/img/experimentalist.png), there is no longer direct correspondence from this language to M, X, Y in an image. not a big deal, just FYI.

[musslick]

Awesome, thank you! Yes, I decided top drop the formal language; I think it overcomplicates things and is harder to track for consistency across the different module types.

[younesStrittmatter]

looks good