ModGC

use the narrower of Class and Module #2660

Job	Run time
check (default, macos-latest)	8m 52s
check (mmtk, release, macos-latest)	13m 45s
check (mmtk, release, ubuntu-latest)	11m 13s
check (default, ubuntu-latest)	7m 50s
	41m 40s

Provide feedback