refactors readme and EKS quickstart for bottlerocket.dev

[stockholmux]

Issue number:

Closes # n/a

Description of changes:

QUICKSTART-EKS.md contains both quickstart and manual setup information (slow start?) as well as a number of dated references. With the launch of bottlerocket.dev, the GitHub readme documentation can be migrated. This PR starts the process of directing users to bottlerocket.dev for EKS quickstart info.

QUICKSTART-EKS.md should probably have never had manual setup instructions and bottlerocket.dev currently lacks this level of detail, so those sections are retained in the document for now. Additionally, the file itself is likely hyperlinked all over the place outside of this repo, so it's wise to retain the file for the foreseeable future.

• Points the README links for the EKS quickstart to bottlerocket.dev
• Refactors README references to QUICKSTART-EKS.md to "EKS Setup Guide"
• Refactors the heading hierarchy
• Removes quickstart section from QUICKSTART-EKS.md and points to the evergreen link on bottlerocket.dev.

Testing done:

Eyeballs only.

Terms of contribution:

By submitting this pull request, I agree that this contribution is dual-licensed under the terms of both the Apache License, version 2.0, and the MIT license.

[webern]

We do rebases instead of merging develop into our branch. So try this, assuming bottlerocket-os is the remote named upstream and your fork is the remote named origin.

git checkout develop
git pull upstream develop
git checkout -b fix-readme-update
git cherry-pick 7503f9b6c7b69fc2d2c8c499cfa29bc0aada3785
git push origin -f fix-readme-update:quickstart-readme-update
git fetch origin quickstart-readme-update
git checkout quickstart-readme-update
git reset --hard origin/quickstart-readme-update

Other people will probably chime in with something much more efficient.