quickstarts in optaplanner distribution zip alongside examples

On optaplanner.org the big green button downloads the optaplanner distribution zip.

Currently that distribution zip is build with this assembly
https://github.com/kiegroup/optaplanner/blob/main/optaplanner-distribution/src/main/assembly/assembly-optaplanner.xml
This zip contains javadocs, reference manual, etc

We also have 2 quickstarts-distribution zips (binaries + sources) build from this assembly:
https://github.com/kiegroup/optaplanner-quickstarts/tree/stable/build/quickstarts-distribution/src/main/assembly
These zips are not shipped yet.

We want to end up with 1 distribution zip linked from optaplanner.org's green button.

1) This unified zip should contain:

• Quickstarts
  • Run showcase (without compilation, so the current binaries zip basically)
  • Sources that can be immediatly build from maven (so basically the current sources zip)
• Examples
  • Run examples with shell script
  • Sources that can be immediatly build from maven
• License.txt
• Readme
  • Link to optaplanner documentation
  • Link to upgrade recipes
  • [seperate issue?] As a pretty single-file html page?
    • Use embedded styles to make it a bit pretty?

2) This unified zip dosn't have to contain:

• javadocs (no one reads those there)
• user guide (follow link in readme instead)

3) Do not move optaplanner-examples at this point - this is a separate issue that is pandora's box (integration testing; turtle tests etc).

• This probably means that the optaplanner repo will need to continue to have an assembly, that is consumed by an assembly over at optaplanner-quickstarts... Rename that so it is clear that its not THE distribution zip, but a build intermediate thing.