Remove using declarations in root-cling dictionary files to avoid interpreter clashes with the global namespace

Co-authored-by: Andre Sailer <andre.philippe.sailer@cern.ch>

Use of nicely named variables such as $p may clash with local user
environments. A similar change was implemented in ROOT a long time
ago:
https://github.com/root-project/root/commit/bba80a143655a4aac63cb5adb2e9f2d73bcd9566

Unknown pragma error

there are many overlaps in the model, regardless of unit system used, but sometimes a track can get stuck, this avoids it for the test case