Redo reference

[ianspektor]

New docs structure

Docs now work as follows:

• The structure that the navigation follows is the structure of markdown files under docs/src/reference
• If a file there has content, the code ref generator doesn't touch it. Keep in mind you can still use mkdocstring identifiers (e.g. ::: temporian.to_csv) for them to be auto-filled with that symbols' docstring. More info here.
• If the file is empty, it is interpreted as a placeholder for the top-level symbol with its same name and its reference page is generated in its same path. E.g., if an empty docs/src/reference/temporian/io/to_csv.md file exists, the reference page for temporian.to_csv will be generated under reference/temporian/io/to_csv/ in the docs.

Tests

Added two tests:

• One that checks that the symbols available in temporian. are exactly the ones we expect
• One that checks that all of those symbols have an auto-generated page in the reference folder (so that we don't forget adding it when adding a new symbol)

Bonus

• Managed to remove the tp.core, tp.implementation, etc. symbols by simply doing del core in the init file 👀
• Ordered the symbols in the left nav alphabetically + folders at the bottom

[DonBraulio]

This reference is ✨✨✨

[achoum]

LGTM

[achoum]

What about adding a comment that tell that this script is executed when running mkdocs serve -f docs/mkdocs.yml?

[achoum]

This front page is now awesome.