means for m2e to set system properties for some tests

There needs to be a means for m2e to advise the Eclipse IDE testing subsystem of system properties to make available to unit tests when run within the IDE.

Both the [Maven Surefire Plugin](https://maven.apache.org/surefire/maven-surefire-plugin/test-mojo.html#systemPropertyVariables) and the [Maven Failsafe Plugin](https://maven.apache.org/surefire/maven-failsafe-plugin/integration-test-mojo.html#systemPropertyVariables) provide a `` as way to configure system properties that will be accessible for unit test and integration tests, respectively. See [Using System Properties](https://maven.apache.org/surefire/maven-surefire-plugin/examples/system-properties.html) for an example.

IntelliJ apparently (see [IDEA-101185](https://youtrack.jetbrains.com/issue/IDEA-101185)) supports `` in in-IDE tests.

Unfortunately Eclipse IDE ignore any `` properties set in the Maven POM in these plugin configurations. In the discussion in eclipse-m2e/m2e-core#174, I was told that m2e, when in processes a Maven POM, has no way to advise Eclipse of the system properties to be used for in-IDE testing. I was [asked](https://github.com/eclipse-m2e/m2e-core/issues/174#issuecomment-1602842656) to file a ticket here to request this capability. Otherwise, our `` properties are ignored in unit/integration tests and according to m2e, they have no way around this.