The picocli-groovy module should declare groovy-all as dependency

[remkop]

History: the picocli.groovy package used to be bundled inside the picocli.jar, until it was split off into a separate artifact picocli-groovy in version 4.0.

It was not desirable (#232) for the picocli.jar to depend on groovy-all (there was a version 2.0.2 published that had this dependency), and this dependency was removed in picocli 2.0.3.
In picocli 2.0.3, the groovy-all dependency was changed to a compileOnly dependency.

This compileOnly build configuration was retained even when the picocli.groovy packages were moved into the separate picocli-groovy module.

The POM for picocli-groovy now looks like this:

  <groupId>info.picocli</groupId>
  <artifactId>picocli-groovy</artifactId>
  <version>4.6.3</version>
  <name>picocli-groovy</name>
  <!-- ... -->
  <dependencies>
    <dependency>
      <groupId>info.picocli</groupId>
      <artifactId>picocli</artifactId>
      <version>4.6.3</version>
      <scope>compile</scope>
    </dependency>
  </dependencies>

This is incorrect, since various classes in the picocli.groovy packages expose Groovy APIs.
From 4.7.0, the picocli-groovy POM will reflect this:

  <groupId>info.picocli</groupId>
  <artifactId>picocli-groovy</artifactId>
  <version>4.7.0-SNAPSHOT</version>
  <name>picocli-groovy</name>
  <!-- ... -->
  <dependencies>
    <dependency>
      <groupId>info.picocli</groupId>
      <artifactId>picocli</artifactId>
      <version>4.7.0-SNAPSHOT</version>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>org.codehaus.groovy</groupId>
      <artifactId>groovy-all</artifactId>
      <version>2.4.21</version> <!-- this is the minimum version. Any higher version also works. -->
      <scope>compile</scope>
    </dependency>
  </dependencies>

This also aligns the Maven dependency in line with the module-info declaration:

module info.picocli.groovy {
    requires info.picocli;
    requires groovy.all;

    exports picocli.groovy;
}