fast_deepcopy_system: fix shared units references bug

src/base.jl

@@ -2696,5 +2696,9 @@ function fast_deepcopy_system(
         time_series_directory = deepcopy(sys.time_series_directory),
         name = deepcopy(sys.metadata.name),
         description = deepcopy(sys.metadata.description))
+    # deepcopying sys.data separately from sys.units_settings broke the shared units references, so we have to fix them here
+    for comp in iterate_components(new_sys)
+        comp.internal.units_info = new_sys.units_settings
+    end
     return new_sys
 end

test/test_system.jl

@@ -429,6 +429,10 @@ end
                 [:time_series_manager, :supplemental_attribute_manager][[skip_ts, skip_sa]],
             ),
         )
+
+        # We copy the SystemData separately from the other System fields, so the egal-ity of these references could get broken
+        generator = get_component(ThermalStandard, sys2, "322_CT_6")
+        @test sys2.units_settings === generator.internal.units_info
     end
 end