Eliminate duplicate documentation on creating new repositories when upstream forks

[sxa]

We currently have:

• https://github.com/adoptium/temurin-build/wiki/Creating-new-jdkNNu-(updates)-repro-mirror-from-the-jdkNN-release-mirror
• https://github.com/adoptium/temurin-build/wiki/Setting-up-new-build-jobs,-mirrors,...-when-a-new-openjdk-version-is-branched-from-jdk(head)

This is confusing and they need to be unified to ensure mistakes are not made. From my perspective there are a few things that I want to add based on my experience in this cycle. There will also need to be information on the API updates required (see this PR) and probably also anything additional required to get the new nightlies added onto the drop downs on the adoptium.net website.

Additional updates (feel free to add to this list):

• Ensure links to the skara mirror jobs are correct
• Information required about the ea trigger jobs

Sample otterdog PR: adoptium/.eclipsefdn#38

Please describe what you want to be able to do that isn't documented, and/or what you'd like to see in the documentation.

[sxa]

May need some further updates, but this is now funcamentally complete. I've left the old wiki page in place for now as reference, but that should be removed as well - most likely in April once we've gone through the January and March releases.