Remove obsolete code to download JDK from Adoptium website

[andsel]

Release notes

[rn:skip]

What does this PR do?

Remove the dead code to download JDK binaries from the Adoptium website. Updates also the versions.yml to reflect this change and permit the selection of just major number of a JDK, the full version is extracted from Elastic's JDK registry.

Why is it important/What is the impact to the user?

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [ ] I have made corresponding change to the default configuration files (and/or docker env variables)
• [ ] I have added tests that prove my fix is effective or that my feature works

Author's Checklist

• tested locally

How to test this PR locally

Run the command:

./gradlew clean downloadJdk -Pjdk_bundle_os=darwin -Pjdk_arch=arm64

Related issues

• Closes Remove the support code to download JDK from Adoptium #16344

Logs

(main) % ./gradlew clean downloadJdk -Pjdk_bundle_os=darwin -Pjdk_arch=arm64
To honour the JVM settings for this build a single-use Daemon process will be forked. For more on this, please refer to https://docs.gradle.org/8.7/userguide/gradle_daemon.html#sec:disabling_the_daemon in the Gradle documentation.
Daemon will be stopped at the end of the build
Retrieving JDK 21 from catalog...
Retrieved! Download path: /jvm-catalog.elastic.co/adoptiumjdk-21.0.4_7-darwin-aarch64.tar.gz

[elastic-sonarqube]

Quality Gate passed

Issues
0 New issues
0 Fixed issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
No data about Duplication

See analysis details on SonarQube

[elasticmachine]

💚 Build Succeeded

• Buildkite Build
• Commit: 1834310

cc @andsel

[kaisecheng]

I am wondering can we keep the old path in case we need to pin jdk version for quick fix/ release. I believe most of the time using the version from the endpoint is fine. When revision, vendor and build is defined, they take precedence.