Update the usage of SciJava common's TestUtils

Partially, this PR works around a bug in scijava-common 2.20.0 (which is too minor to merit a new pom-scijava version, although it triggered the release of 2.20.1), partially it makes use of new and improved features offered by the `TestUtils` class.

It also bumps the parent version preemptively (and as such requires imagej/pom-imagej#1 to be addressed first).