net/activemq: Update 6.2.0 => 6.2.4, take maintainership
Release Notes:
https://activemq.apache.org/components/classic/download/classic-06-02-01
https://activemq.apache.org/components/classic/download/classic-06-02-02
https://activemq.apache.org/components/classic/download/classic-06-02-03
https://activemq.apache.org/components/classic/download/classic-06-02-04
Improve port:
- Adjust JAVA_VERSION.
- Add substitution instead of hardcoded USER and GROUP in rc script.
PR: 294136
Approved by: blanket (3rd in a row maintainer timeout during last 2.5 years)
Sponsored by: UNIS Labs
MFH: 2026Q2
(cherry picked from commit 8f41140a8cc479a9c574d06fa314b25051174d95)