CI: test with java 23

[pjfanning]

Java 22 is not LTS and Java 23 is out. Java 23 contains a fix for #4848 so it is useful to know if this module works ok with Java 23.

[pjfanning]

• there are some test issues on Java 23
• the main issue seems to be that mockito 4.11.0 doesn't seem to work in all cases on Java 23
  • mockito 5 needs newer Java version
  • might be able to fix the build so that it uses Mockito 5 for newer Java versions but 4.11.0 for Java 8
• there may be 1 or 2 other test issues too

[pjfanning]

#4856 is needed for this to work and possibly more changes too

[cowtowncoder]

@pjfanning Thanks, merging other PRs and hopefully that is enough to make JDK 23 variant pass.