Migrated to Log4j2

Summary

• Updated the dependencies that actively do logging (the snmpman-cli module and the unit tests) to use log4j2 instead of the end-of-life log4j1.
• Updated testng 6 to 7.
• Updated the jackson library version used.

What do you need to do for migration?

snmpman-cli users

If you're using the command line version of snmpman, you need to adapt your setup to provide a log4j2.xml configuration (or take the one provided with the jar).

snmpman (library) users

Library usage (the snmpman module itself without snmpman-cli) is still logging using slf4j. No changes needed if you already have a slf4j plugin in use.