Moving from JLine2 to JLine3 for leshan-client-demo Interactive commands.

[sbernard31]

JLine 2 was chosen because :

• we targeted Java7 as minimal runtime.
• JLine 2 use Java5 as minimal runtime.
• JLine 3 use Java8 as minimal runtime.
• Picocli provide library to work with JLine 2 (picocli-shell-jline2).

But :

• For Leshan 2.x, we moved to Java8 (Which minimal version of java for Leshan 2.0.0 ? #924 (comment))
• "JLine 2.x development has come to an end, and users are encouraged to investigate the use of JLine 3.x instead." (from jline/jline2 (README))
• Picocli also provides library to work with JLine 3.(picocli-shell-jline3)

So, we should probably consider to seriously move from JLine 2 to JLine 3. 🤔
An old "work in progress" is available at : #1065