Add implementation for signal handling. Use generic signal handler in DDG4 for controlled shutdown on CTRL-C. Add test DDG4_SIGINT_handler in examples/DDG4

Add implementation for signal handling. Use generic signal handler in DDG4 for controlled shutdown on CTRL-C. Add test DDG4_SIGINT_handler in examples/DDG4

ROOT no longer finds nlohmann_json unless we ask for the ROOTEve
component, so we ask for the ROOTEve component if the ROOTEve
component exists.  DDEve and one executable in UtilityApps depend on
this

fixes some tests that can run in this case successfully now

test_import: change error to fehler to avoid triggering test failure because we get a warning from gosam

conditions: use static unsigned long long int because ROOTs latest llvm otherwise causes assertion in debug mode about not being able to represent in 64 bit. Not sure if bug in enum parsing???

Add warning if TGeo materialScan hits TGeoTessellated volumes. See github issue https://github.com/AIDASoft/DD4hep/issues/1322

Too much hassle to ensure that the list was not duplicating the entries in the list

The original implementation also caused infinite loop by appending to the list that was iterated over causing ddsim to use up all the memory and not do anything

Added a test with an example ddsim steering file

Speeds up by 50 percent the construction in fiber dual readout calorimeter with 580k volumes (108 s down to 68 s on my machine)