8027643: Merge GenCollectorPolicy and TwoGenerationCollectorPolicy
Summary: Merged the two calsses GenCollectorPolicy and TwoGenerationCollectorPolicy
Reviewed-by: sjohanss, jcoomes
8042570: Excessive number of tests timing out on nightly testing due to fix for 8040798
Summary: Remove unnecessary lock in CompileBroker::mark_on_stack() that causes the deadlock
Reviewed-by: kvn, dcubed