This is a new mallopt option that will force purge absolutely
everything no matter how long it takes to purge.
Wrote a unit test for the new mallopt, and added a test to help
verify that new mallopt parameters do not conflict with each other.
Modified some benchmarks to use this new parameter so that we can
get better RSS data.
Added a new M_PURGE_ALL benchmark.
Bug: 243851006
Test: All unit tests pass.
Test: Ran changed benchmarks.
Change-Id: I1b46a5e6253538108e052d11ee46fd513568adec
This benchmark also includes the measuring of RSS.
Bug: 137795072
Test: Ran different iterations and verified the RSS_MB value is nearly
Test: identical no matter the number of iterations.
Change-Id: I465a0eae9dcff2e1fb739c35623a26291680951f
