Catch2Tests: Collect DEBUG logs from test process and servers

This is intended to help debug failing tests by collecting logs from all the processes involved.

A single log file is created for a test run and every process logs to this same file, which a prefix so we can distinguish each process. You can add your own logs with the normal TANGO_LOG_DEBUG macro from either the test or the device servers.

The logs are added as artefacts to the CI test jobs.

This doesn't quite do what #1235 (closed) asks, however, the "server logs" (which are just the redirected output of the server processes) are used by the test harness and must be separate for each device server. In my opinion, this makes these files not very useful for debugging.

Having a dedicated log file means we can see when events in different processes happen relative to each other and we can add logs from the tests.

Closes #1235 (closed).