Add an operation performing non-moving allocation in ThreadStress.

ThreadStress already has an `Alloc` operation, allocating in the
main (moving) space and a `LargeAlloc` operation, allocating in the
Large Object Space (LOS). This change adds a `NonMovingAlloc`
operation, allocating in the non-moving space (using
dalvik.system.VMRuntime.newNonMovableArray), in order to exercise the
non-moving space.

Relevant default frequency maps are also adjusted to make room for
`NonMovingAlloc` operations.

Test: art/test/testrunner/testrunner.py -t 004-ThreadStress
Change-Id: Ic2fcc0eea81b03d190a540ec31d0c9855881b433