feat(mqtt): MosquittoContainer: Add version 2.1.2 (#978)

This PR enables the testcontainer MosquittoContainer (which I
contributed to this project a few years ago) to work with version 2.1.2
and higher of Mosquitto.

In particular this PR is fixing an issue where rw mode is now needed for
/data partition for Mosquitto version 2.1.1 (released 2026-02-04), which
fixed a PUID/PGID issue.
In addition, it contains a fix for Mosquitto warnings generated by the
`listener` directive appearing after `protocol` directive.