Optimizing: Clean up `#include`s for `HOptimization`.

And change the function `OptimizationPassByName()` to take
a `std::string_view` argument instead of `std::string`.

Test: m test-art-host-gtest
Test: testrunner.py --host --optimizing
Flag: EXEMPT refactor
Change-Id: I49f583f4563dffb1ae2b9f488850ac6656748ac6