Make PassThroughInputManager sync with parent input state

[ekrctb]

When UseParentInput is true, a PassThroughInputManager syncs its keyboard and joystick state to parent InputManager's state.
For mouse buttons, only input that reached event handlers (OnMouseDown and OnMouseUp) are applied. Click initiated at outside of the PassThroughInputManager and blocked inputs are not synced. However, always sync MouseUp to maintain an invariant (for a mouse button) this.pressed <= parent.pressed. This is because a mouse inputs are positional and this behavior is matching to regular Drawables.

• Closes PassThroughInputManager needs to receive initial state from parent #1672
• When KeyBindingContainer handles OnKeyDown before KeyBindings are set there was a null reference. I fixed this. However, the new KeyBindingContainer doesn't fire actions that is bind to keys pressed while the new KeyBindingContainer is initialized. For example, when entering osu!catch play while pressing an arrow key, the catcher isn't moving initially. I think this is allowable but maybe should fix if people need.

[ekrctb]

I originally thought it is good to reset input state when UseParentInput becomes false but I now think not resetting is more natural and sometimes useful.
An issue for current implementation is the input state is not reset even if we do UseParentInput = false when it is already false.

[peppy]

Good job on this one. It's feeling quite solid. Make sure to claim the bounty on the original issue.