RFR: 7861: Bump Agent build to Java 11 compliance and cleanup POM [v2]

[Christoph Langer]

On Thu, 20 Oct 2022 15:10:33 GMT, Christoph Langer <clanger at openjdk.org> wrote:

>> The JMC Agent project is set up in a somewhat awkward way at the moment. The maven.compiler.source and maven.compiler.target properties are set to 1.8 but we enforce a JDK 11 during the build and also have a test case that implicitly uses/tests JDK11 features. Maybe it is time now to bump the agent to Java 11 compliance?
>> 
>> Furthermore, the POM file could be cleaned up and a few maven plugins that are used could be bumped to more recent versions.
>
> Christoph Langer has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains one additional commit since the last revision:
> 
>   Cleanup JMC agent pom

Thanks for the review. I merged master and deleted the .gitignored org.eclipse.jdt.core.prefs file. When checks pass I will integrate.

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PR: https://git.openjdk.org/jmc/pull/415