Merge pull request #21409 from morganchristiansson/ser2net

This major update not only updates the ser2net daemon version,
but also migrates the UCI configuration handling to the newer
YAML configuration file format.

If you only configured ser2net using UCI, then there should
be no noticable difference and your configuration should
still work as before.

If you modified /etc/ser2net.conf before, or used custom adaptions
etc., then you must migrate to newer /etc/ser2net.yaml on your
own and/or double-check your installation - there is no automatic
migration logic during package upgrade path.