Improve CI builds

[iaik-jheher]

• Do not bundle JRE (cf. #20), fall back to system JRE
• Stop double zipping by Github pipe
• Do not build a installer JAR for Linux

[iaik-jheher]

temporarily rebased this on pdf-over-4.4.2 until #26 is resolved, this should allow runners to succeed

[iaik-jheher]

ready for merge, blocked by #26, needs rebase