=== Make OpenJDK 21 the default JAVA_VERSION

Links:
link:https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=272855[Issue 272855] URL: link:https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=272855[] +
link:https://docs.google.com/spreadsheets/d/17hmRQ0ShY4SHHVEkQBVxqK2G88fPZLriTzO26zXdjC4/edit?usp=sharing[Sheet tracking Work in Progress] URL: https://docs.google.com/spreadsheets/d/17hmRQ0ShY4SHHVEkQBVxqK2G88fPZLriTzO26zXdjC4/edit?usp=sharing

Contact: Ronald Klop <ronald@FreeBSD.org>

The default JAVA_VERSION in FreeBSD ports is still OpenJDK 8.
It is time to upgrade this to a more modern version like OpenJDK 21.
We need to test and fix all ports using Java to build or run with JDK 21, or pin JAVA_VERSION in the port to the latest supported version.

The work is being tracked in PR 272855 and a Google Sheet for more details.
Already more than half of the ports that failed a test run is fixed.

If you have experience with Java and the ports system you are invited to help.
I think it is reasonable to have the ports in shape for the JAVA_VERSION=21 setting in February 2026.

Plan:

* Check the last 12 ports and create a PR or commit
* Commit the PRs that are timing out on maintainer feedback
* Ask for another exp-run
* If done, increase JAVA_VERSION
