Multi-version plotting & SMOKE_TEST

[AVHopp]

This PR introduces including plots in the examples in light and dark version.

The requirement is that suitable .svg files are contained in the corresponding example folders. These need to be named like the example itself, together with "_light" and "_dark". Note that both of these files need to be present.
In addition, this PR changes the botorch_analytical.py example to show how corresponding files can be created automatically using a pre-defined .json. Furthermore, the file is changed in such a way to demonstrate the use of a SMOKE_TEST environment variable.

[AdrianSosic]

Just a few minor comments

[AVHopp]

@AdrianSosic @Scienfitz I force pushed the newest version. Please have a very quick look if this is gucci for you and ping me if this can be merged. Explicitly re-asking due to the upload of the svg files and how the potential override of files is handled.

[AVHopp]

@AdrianSosic I am finally done with this. Some things have changed a bit:

1. The plots are not created if SMOKE_TEST is set, the function then just returns: If we just want to test the code, there is no need to create plots. Also, this avoids some complicated handling of the paths and stuff due to the files being executed as python files and jupyter files.
2. I have included a warning if no kwargs are given.
3. There was a mypy import error that I did not undestand completely. I included an ignore_missing_imports and hope that this was done in the correct way. Please check!
4. When running tox locally, there was some error regarding the import of the baybe.plotting submodule.

If you are happy with the current version, feel free to just merge.

[AdrianSosic]

Hey @AVHopp, due to the new changes, there a couple (minor) open issues.

[Scienfitz]

resetting the review and will reevaluate

[AdrianSosic]

Will simply approve to unblock you. There's one minor open issue with the lazy imports that you guys still need to figure out. Other than that, I didn't fully follow your other conversations because of my absence, so I'll simply trust you there ;)