GC triggering performance optimizations.

Copy the correct starting heap size at process init.
Interfaces to set GC/managed heap parameters.

Change-Id: Ia2b158aa28254d88f68c9534a0eef580aa811b10
(cherry picked from commit 60c25a585aaa81496e83fb134502594caa0dceb6)
(cherry picked from commit 8873acb0ffc224388eeadc7204ddb6bff4819c7f)
(cherry picked from commit 6ca5469d1fbfb432a945df49e276fc4edc1eff87)