chore: apply workaround for @In malfunction in actions

[jdrueckert]

Contributes to MovingBlocks/Terasology#4981

What this PR does

Use initialization in construct() consistently throughout behavior actions

@Override
public void construct(Actor actor) {
    if (world == null) {
        world = CoreRegistry.get(WorldProvider.class);
    }
}

• this will work if @in has no effect, i.e., the field is initialized to null
• this will work if @in is fixed and initializes the field correctly, making the code in construct a no-op
• we preserve the information that we want to use @in in actions

Additional chores

• format prefabs (JSON)
• minor code simplification recommended by intellij in CheckAttackStopAction action

[jdrueckert]

FlexibleMovement as a replacement for PathFinding