[IA] Relocate Java Automatic pages to new Zero-code section + other page rework

[chalin]

Contributes to the following for Java:

• [IA] Zero-code as top-level section #4427

Tasks

• Minimal changes, "just" relocate pages
• Canonicalize all links (drop temporary link-checker rule) - [IA] Zero-code Java Agent: canonicalize links + copyedits #4565
• Ensure that dynamic front-matter parameters get auto-updated too in content/en/docs/zero-code/java/_index.md -
  [CI] [Java agent] Ensure pkg versions get updated under zero-code #4569
• Adjust CODEOWNERS
• Page-relative aliases in the Java agent pages need to be fixed too. Those page-relative aliases made sense in the context of the old paths (find out when those aliases where added and hard-code the old paths in replacement of "..") -
  [Java agent] Use absolute alias paths matching original #4568
• Add a placeholder under the old SDK Java section redirecting to the new Automatic section?

@svrnm @zeitlinger - let's use this issue to track all the reorg and page additions

[chalin]

All done, closing.