8206467: Refactor G1ParallelCleaningTask into shared
Summary: Refactored and moved G1ParllelCleaningTask to be shared among GCs
Reviewed-by: rkennke, kbarrett
^build/
^dist/
^.idea/
nbproject/private/
^webrev
^.src-rev$
^.jib/
\.DS_Store
\.metadata/
\.recommenders/
test/nashorn/script/external
test/nashorn/lib
NashornProfile.txt
.*/JTreport/.*
.*/JTwork/.*
.*/.git/.*