Draft: tests/environment/setup_database.sh.cmake: Increase number of files for mysql container

Since the upgrade to debian trixe the machine of the developer of this commit can't run the tests in parallel anymore as it always runs out of memory and the OOM-killer kicks in.

The internet found 1 which says

The bug you found put me on the right tracks. The issue is caused by the ulimit nofile. By default, on arch, the value is too low I guess. running the container with --ulimit nofile=262144:262144 solve the issue and mysql behaves normally. I guess the best way to fix this would be to set this option by default.

and that fixes it here.

Close #1570