feat: editorial review: Update cookie docs

[chrisdavidmills]

Description

#31848 contains the engineering technical review for my work on updating the MDN cookie docs, which has been completed and approved. Thank you to @samdutton for your thorough and detailed review work.

This is a new PR based on the same branch, which is intended to contain the editorial review for the same work.

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Background information

This PR updates some of the cookie information found on MDN, according to the cookie docs proposal that was made available a while ago.

While this PR doesn't make all of the changes listed in the proposal doc, it does the following:

• Update the HTTP cookies guide to clean up the structure a bit, modernize the information, and move some of the information to other places.
• Add a new Third-party cookies article to provide a single detailed definition of 3PC, the issues associated with them, and how to handle those issues.
• Clean up the Privacy landing page to remove some of the browser-specific information, move some of the content to more appropriate places, and generally clean up/improve.
• Update all the pages that provide their own definition of third-party cookies/tracking and link them to the one single definition on the new 3PC article instead.

Motivation

Additional details

Related issues and pull requests

[chrisdavidmills]

In addition to the inline comments, we need to double-check if the drawio files can be stored there. I hope this, but I don't remember the outcome of a former discussion (@bsmth: do you remember?)

Thanks a lot for checking. Could we please move them to https://github.com/mdn/shared-assets/tree/main/images/diagrams? There is also GH pages active on that repo, so you can reference images / SVG like: https://mdn.github.io/shared-assets/images/examples/balloon-small.jpg

Related discussions:

* https://github.com/orgs/mdn/discussions/94

* https://github.com/orgs/mdn/discussions/631#discussioncomment-8222396

Ah, thanks a lot for bringing this to my attention, @teoli2003, and thanks for the info, @bsmth. This discussion completely passed me by; I am really glad we have a place for shared images now!

I will immediately put my image files on the shared-assets repo, before I continue with the rest of the work in this PR.

[chrisdavidmills]

@teoli2003 thanks for the fabulous review. I've responded to everything now. Back to you!

[teoli2003]

Sounds good to me.

Thank you!