Remove dependency between free collection set and eagerly reclaim humongous object tasks

After the free collection set task there is a phase where the free list is rebuilt. After that the eagerly reclaim humongous objects task adds to that (recently rebuilt) free region list.

This dependency is not necessary. Just put the rebuild of the free region list after eager reclaim, without the eager reclaim doing nothing particular about the freed regions.

This helps JDK-8214237, merging phases into less parallel phases.