Properly scope HLoopOptimization's allocator.

HOptimization classes do not get their destructor called,
as they are arena objects. So the scope for the optimization
allocator needs to be the Run method.

Also anticipate bisection search breakage by adding
HLoopOptimization to the list of recognized optimizations.

Change-Id: I7770989c39d5700a3b6b0a20af5d4b874dfde111