Remove the experimental option UseCGroupMemoryLimitForHeap?

[linzang(臧琳)]

Dear All,
                I would like to discuss with you whether the experimental option “UseCGroupMemoryLimitForHeap” is unnecessary now?
                I see there is only one place in the code using this flag, and the logic there is considering cgroup memory limit when calculating heap size, but it is duplicated with os::physical_memory() since there is same implementation for container support.
                So is it ok if I remove this flag?

BRs,
Lin