Made KfComponentsHolder thread safe

Changed the dummy function static to be thread_local since different
threads were changing the value simultaneously.
Only forward declare KfComponentsHolder in TrackingRecHit.h

TrackingRecHit.h only needs a forward declaration of KfComponentsHolder.
Fixed the few cases where the include was explicitly needed.
Merge pull request #3734 from Dr15Jones/makeKfComponentsHolderThreadSafe

MT -- Make KfComponentsHolder thread safe