Hide verbose dart snapshot during run_test.py (#11040)
Hide verbose dart snapshot during run_test.py (#11040)

Without this change, a single dart test will print out 306 lines.
With this change, a single dart test will only print out 33 lines.
This helps a lot in local tests.

In order to return to the old logging, set `--verbose-dart-snapshot` flag.
chinmaygarde/flutter_engine,tvolkert/engine,aam/engine,Hixie/sky_engine,chinmaygarde/sky_engine,jamesr/sky_engine,mikejurka/engine,chinmaygarde/flutter_engine,jason-simmons/sky_engine,cdotstout/sky_engine,chinmaygarde/sky_engine,flutter/engine,mikejurka/engine,mikejurka/engine,devoncarew/engine,jason-simmons/flutter_engine,jason-simmons/sky_engine,mikejurka/engine,flutter/engine,devoncarew/engine,jamesr/sky_engine,Hixie/sky_engine,jamesr/flutter_engine,flutter/engine,jason-simmons/sky_engine,flutter/engine,jason-simmons/flutter_engine,cdotstout/sky_engine,chinmaygarde/flutter_engine,jason-simmons/sky_engine,rmacnak-google/engine,chinmaygarde/flutter_engine,rmacnak-google/engine,jamesr/flutter_engine,tvolkert/engine,rmacnak-google/engine,jamesr/sky_engine,devoncarew/sky_engine,tvolkert/engine,aam/engine,jamesr/sky_engine,Hixie/sky_engine,aam/engine,rmacnak-google/engine,Hixie/sky_engine,chinmaygarde/sky_engine,jamesr/flutter_engine,aam/engine,jamesr/sky_engine,flutter/engine,Hixie/sky_engine,jason-simmons/flutter_engine,rmacnak-google/engine,cdotstout/sky_engine,jamesr/sky_engine,devoncarew/sky_engine,devoncarew/engine,cdotstout/sky_engine,tvolkert/engine,aam/engine,jason-simmons/flutter_engine,jamesr/flutter_engine,jason-simmons/flutter_engine,tvolkert/engine,flutter/engine,jason-simmons/flutter_engine,jamesr/flutter_engine,tvolkert/engine,aam/engine,jason-simmons/sky_engine,chinmaygarde/sky_engine,devoncarew/engine,Hixie/sky_engine,Hixie/sky_engine,aam/engine,mikejurka/engine,devoncarew/sky_engine,jamesr/flutter_engine,chinmaygarde/sky_engine,flutter/engine,chinmaygarde/sky_engine,jamesr/flutter_engine,jason-simmons/flutter_engine,chinmaygarde/flutter_engine,cdotstout/sky_engine,devoncarew/sky_engine,jamesr/sky_engine,mikejurka/engine,Hixie/sky_engine,aam/engine,devoncarew/sky_engine,cdotstout/sky_engine,devoncarew/sky_engine,mikejurka/engine,mikejurka/engine,chinmaygarde/sky_engine,jason-simmons/flutter_engine,chinmaygarde/flutter_engine,flutter/engine,jason-simmons/sky_engine,devoncarew/engine,jason-simmons/sky_engine,jamesr/flutter_engine,devoncarew/engine,tvolkert/engine,devoncarew/sky_engine,cdotstout/sky_engine,jamesr/flutter_engine,rmacnak-google/engine,mikejurka/engine,chinmaygarde/flutter_engine,devoncarew/engine,rmacnak-google/engine