[docs] Updates starter pack & enables GA

[afgambin]

This PR:

1. It updates the starter pack to the latest version: You will see a lot of changes in the docs directory. It is working now as expected, all checks have passed.
2. It enables Google Analytics and adds a cookie banner as per requested from the Web team.
   It is part of this Jira ticket: https://warthogs.atlassian.net/browse/KF-7607

You can test the PR by checking the Docs build in the CI below (docs/readthedocs entry) or run it locally by making make clean & make run. You should see the added cookies banner + the new starter pack format.

[mvlassis]

Tried locally on my machine and everything renders as expected. I found some nitpicks, but will create changes in the starter pack repo so that they are propagated.

Also note that the cookie banner is rendered in the exact middle of the screen, I'm not sure if that is expected or that should be in a different place (e.g. bottom).

[SecondSkoll]

Also note that the cookie banner is rendered in the exact middle of the screen, I'm not sure if that is expected or that should be in a different place (e.g. bottom).

The placement attempts to replicate the same placement on ubuntu.com and canonical.com.

And as per my comment in the ml-flow PR, .github/workflows/sphinx-python-dependency-build-checks.yml is only needed in your documentation if you have specific customisations to your build and you have a need for your documentation (and doc deps) to be built from source.

[afgambin]

Thanks @SecondSkoll for the input! Removing that workflow then.