Run system tests in parallel

[patchwork01]

Background

Split from:

• Parallelise system tests #1794

Description

We'd like to run all system tests in parallel, so that they should run much quicker overall.

Analysis

We could look at options to get the Failsafe Maven plugin to parallelise the tests, but looking at the documentation it doesn't seem clear that this will work.

We could look at ways to invoke JUnit directly, maybe from a main method.

We'll want logging to happen independently for each test if possible, to separate files in the output directory.

We need to make sure we've covered everything that might not be thread safe before we do this, e.g.:

• Thread safety when connecting to instances in system tests #3775