Enable the Web process cache on iOS by addressing an issue where the physical memory size in GB is reported as zero, causing the process cache capacity to be set to zero. This is because the jetsam limit is taken into consideration in this computation on iOS. This patch adds a function that returns the memory size without considering the jetsam limit of the calling process. Additionally, when a cached WebContent process is suspended, we should not release the memory immediately, since keeping this memory is a speedup when the cached process is being used again. This change is a speedup on page load benchmarks.