[SUREFIRE-2139] Raise plexus-java to 1.1.2 for proper Java 19/20 bytecode support

[andpab]

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[olamy]

We could/should change to use the asm bom.

[andpab]

We could/should change to use the asm bom.

Done.

I've also added a commit to replace JDK18 which is EOL by now with JDK19 in the builds, partly to demonstrate that it works with the changes I made. If that build-related change shouldn't be part of this PR, then let me know and I'll drop it.

[andpab]

Well, it's good I did that, because silly me forgot to add the import scope to the asm-bom dependency at first.

Now we should be good.

[andpab]

Thankfully, @slachiewicz has just released a new version of plexus-java which brings asm 9.4. So I'm going to simplify the pull request and just update the plexus-java.version property to 1.1.2 instead.