feat: automatic merge for multi-module projects

[algomaster99]

Fixes #30

We stick to the double command workflow because of #82 (comment).

There are two major changes

1. Only a single merged classport-files is created at the directory when mvn command is run.
2. -Dmaven.main.skip is required flag for packaging. This is necessary because packaging phase writes the MANIFEST.MF file into target/classes directory which triggers a recompilation of the main class for the next submodule in the reactor phase. For a single module project, this -Dmaven.main.skip is not needed. If you do need to compile the main class, you can run mvn compile again.

[algomaster99]

Doing it at packaging time is not the best idea because then the bundled jar is embedded. So classfiles like info.picocli.CommandLine have annotations like this:

    @ClassportInfo(group = "org.apache.pdfbox", version = "3.0.4", id = "org.apache.pdfbox:pdfbox-app:bundle:3.0.4", sourceProjectId = "org.apache.pdfbox:pdfbox-app:bundle:3.0.4", childIds = { "org.apache.pdfbox:pdfbox-tools:jar:3.0.4", "org.bouncycastle:bcpkix-jdk18on:jar:1.80", "org.bouncycastle:bcprov-jdk18on:jar:1.80", "commons-io:commons-io:jar:2.18.0", "org.apache.pdfbox:jbig2-imageio:jar:3.0.4" }, artefact = "pdfbox-app", isDirectDependency = false)
    public interface IExitCodeExceptionMapper
    {
        int getExitCode(final Throwable p0);
    }

The group should be info.picocli.