`java`: Switch datasource

[viceice]

Currently we use https://api.adoptium.net to find the release binaries.
We should switch to use the java-metadata github repo to have less hosts.
Can be done when converting installer to typescript
Maybe we should mirror binaries to our org?

• https://github.com/joschi/java-metadata/blob/main/docs/metadata/ga/linux/x86_64/jre/hotspot/adoptopenjdk.json
• Extend `java-version` datasource renovatebot/renovate#22688
• Document hosts needed for install-tool #717
• Allow all external download URLs to be aliased #1067