Draft: Support newer TBB (incl. Intel oneAPI TBB)

Forwarded from https://github.com/key4hep/Gaudi/pull/3

Main changes:

• Prefer finding TBB through TBBConfig.cmake over the included FindTBB.cmake module
• Remove explicit version from tbb::spin_rw_mutex_v3 (FIXME: needs version check verification)
• tbb/tbb_stddef.h was removed from recent versions
• tbb::task_arena must now be constructed with the threadpool size, so we use a shared_ptr

Status:

• Compiles with newer TBB version but needs must more extensive testing:
  • does the CMake change find the 'right' locations?
  • does this now still work with older TBB and with all newer TBBs?

This should fix #270 (closed)