Toolbox mvnsh integration WIP

[cstamas]

Integrate Toolbox into mvnsh.

Example:

[cstamas@blondie laeubi]$ mvnsh
mvnsh> help
  System:
    exit                   help                   
  Builtins:
    colors                 highlighter            history                keymap                 less                   nano                   setopt                 
    setvar                 top                    unsetopt               widget                 
  Maveniverse Toolbox:
    artifact-path          classpath              copy                   copy-gav               copy-recorded          copy-transitive        deploy                 
    deploy-recorded        dm-list                dm-tree                dump                   effective-model        exists                 identify               
    install                libyear                list                   list-available-plugins list-repositories      local-repository-path  metadata-path          
    record                 repl                   resolve                resolve-transitive     search                 tree                   verify                 
    versions               
  Builtin Maven Shell commands:
    mvn                    mvnenc                 
mvnsh> 

Note: as jline is not exposed, this .mvn/extenions.xml should be used:

<?xml version="1.0" encoding="UTF-8"?>
<extensions>
    <extension>
        <groupId>eu.maveniverse.maven.plugins</groupId>
        <artifactId>toolbox</artifactId>
        <version>0.6.1-SNAPSHOT</version>
        <classLoadingStrategy>parent-first</classLoadingStrategy>
    </extension>

Needs apache/maven#1982