Increase required Java version?

[Martin Desruisseaux via dev]

Hello all

For the next release of SIS, should we increase the minimal Java version 
required by the endorsed modules? The current version is Java 11. We 
could target Java 17 or 21. If agreed, I propose to start with only Java 
12 for SIS 1.8 and move to the high version afterward. The reason for 
one conservative step is because some users wanted strongly a low 
minimal version in the past, and they may not be following this mailing 
list. Doing one step at Java 12 will give us a chance to see if it 
causes some reaction after the next SIS release before more substantial 
changes.

Note: this proposal has no impact on the "incubator" group of modules, 
which is already on a higher Java version.

    Martin