4.x: explicitly configure javac for annotation processing

[barchetta]

Environment Details

• Helidon Version: 4.0.0-SNAPSHOT (24-Aug-2023)
• Helidon SE or Helidon MP: MP
• JDK version: openjdk 21-ea 2023-09-19

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Problem Description

When compiling the Helidon 4 MP quickstart application (and the Helidon project itself) you see the following message:

  Annotation processing is enabled because one or more processors were found
  on the class path. A future release of javac may disable annotation processing
  unless at least one processor is specified by name (-processor), or a search
  path is specified (--processor-path, --processor-module-path), or annotation
  processing is enabled explicitly (-proc:only, -proc:full).
  Use -Xlint:-options to suppress this message.
  Use -proc:none to disable annotation processing.

This is due to a change in Java 21. See:

• https://inside.java/2023/07/29/quality-heads-up/
• https://bugs.openjdk.org/browse/JDK-8310061

We should explicitly configure javac to eliminate this message.