Change: forcefully enable prefixing logs with date (#11930)

Additionally, add the log-level to the log message.

Codechange: move regression outside of bin and make it work via CMake script

The tst_stationlist savegame had to be changed to start the correct
AI. In the old setup, all regression AIs had the same name, which
made it impossible to run both regressions in parallel. With the new
setup this is possible.

Although all files are available to run the regression, it won't
really work till CMake is introduced (which will happen in a few
commits from here)