Migration java 21

[dloy]

We are currently running on java 11 with an implementation of java 8. The intention has been to move to java 11 compilation and execution later this year. Premier support for java 11 ended September 2023.

This proposal is that we move to the latest Long Term Support (LTS) version of java, java 21, for implementation, compilation and execution. This premier support should be good through September 2028.

Indications are that most required coding changes forced by recent java upgrades were in versions 9 and 10. We currently appear to be able to move our code to java 11 without additional changes. This predicts we should be able to move to java 21 without requiring code updates (hopefully!).

For java 21 Ashley reports:
AmazonLinux2023 offers rpms for java21. Tomcat docs indicate tomcat9 works with any java 8 or later. I see no issues.
https://tomcat.apache.org/whichversion.html

Amazon Corretto Java 21 is currently available.

[elopatin-uc3]

Ensure we can obtain all supporting tools needed for Java 21 on our development platforms (PC, Linux, Mac).

Consider timing this effort with creation of new dev boxes running on AL2023.