[refactor] Use well_container and PerforationData for tracers

This saves some (expensive?) lookups that already have been done
in the well model. We had to make the well_container accessible from
the well model for this.

Using the perforation data will automatically make sure that the
perforations are not shut and reside on this process in a parallel run.

opm/simulators/wells/WellInterfaceGeneric.hpp

@@ -60,6 +60,9 @@ public:
                          const int index_of_well,
                          const std::vector<PerforationData>& perf_data);
 
+    /// \brief Get the perforations of the well
+    const std::vector<PerforationData>& perforationData() const;
+
     /// Well name.
     const std::string& name() const;