Use HeapGrowthMultiplier for native allocaitons

Reduces the amount of native allocation GCs for foreground apps.
For camera: The number of native allocations GCs goes from 4 to 2,
improving launch time by 25ms (average of 25 runs on pixel).

The multiplier is 1 for low ram devices, so this should not increase
RAM on devices where it matters.

Bug: 36727951
Test: test-art-host

Change-Id: I0b9e090d9d85bcb2fcd24f221988e99b91ec5977