Cache loggers

Avoid reconstructing logger names and getting logers repeatedly (takes more then 10% of simlation timefor the minimal benchworking example).

• Make child loggers use the correct logging level (seems like set too late in composition)
  • Solved (partially) by storing the logger only if base_logger_name is available

Brings the run time for the minimal 1y simulation from 120 ms (after removing time coord) to 105 ms.