Make CORSIKA 8 fast again

Currently we are 10-15 times slower than CORSIKA 7. After discussing with Felix we believe that this is caused by calling SIBYLL for event generation with N or O targets instead of "air" as in C7 and certain tabulated cross-sections are then not used within SIBYLL itself. The preferred solution requires some SIBYLL-internal changes since we probably don't want to go back to the way it was done in C7.