ART: Refactor SchedulingGraph for consistency and clarity

The CL moves functionality from SchedulingGraph to other classes,
deletes unused code and moves code used for testing to the tests source
1. SchedulingGraph::AddDependency: move checks whether a dependency has
been added to SchedulingNode::Add*Predecessor as it is a SchedulingNode
responsibility to keep a unique set of predecessors.
2. Create SideEffectDependencyAnalysis class. Code doing side effect dependency
analysis is moved from SchedulingGraph into the class.
3. Remove SchedulingGraph::HasImmediate*Dependency methods as there are
SchedulingNode::Has*Dependency methods for such kind of checks.
4. SchedulingGraph::HasImmediate*Dependency(HInstruction,HInstruction) methods
are only used by tests. Their code is moved to a new class TestSchedulingGraph in
the tests source file.

Test: --host --optimizing --jit --gtest
Test: --target --optimizing --jit

Change-Id: Id16eb6e9f8b9706e616dff0ccc1d0353ed968367
3 files changed