We used @runInSeparateProcess for some unit tests based on assumptions that either no longer hold true, or can be worked around rather easily.

- In the ConfigServiceLocator, using include instead of include_once makes it possible to drop the tag. IMHO it might even be more correct behavior.
- In the DateTime class, the tag was used because of the impact of setting LC_ALL. I'm still not sure this is without consequences, but passing unit tests prove me otherwise.

The other tests are mostly about the fact the we include files and don't want them to hang around, just in case. I was certain this matters when I wrote them (early on). I changed my mind.

Speedup: ~30 seconds on my local system

Unit tests