GC triggering performance optimizations

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

Change-Id: I454b1985a3225d7dbdea9c5d4e6f0c9f5e24352e
(cherry picked from commit ea59f91c8559dee1710f38a27db10f76f4753fea)
(cherry picked from commit 12fc949d46e988ce6877ad4c60f5fc983c5dc202)
(cherry picked from commit 73a1dac0b14ab5159453c2d696049e233e7476b0)