RFR: Remove dead-weight ShenandoahPrinter

[Aleksey Shipilev]

Long time ago, we have move printing routines to ShenandoahPrinter on the off chance someone would
need them. Apparently, nobody does need them. Let's purge those files from the repo:

$ hg qdiff | diffstat
 shenandoahPrinter.cpp |  107 --------------------------------------------------
 shenandoahPrinter.hpp |   51 -----------------------
 2 files changed, 158 deletions(-)

Testing: tier1_gc_shenandoah

Thanks,
-Aleksey