Fixed getting filtered spatial elements at import for ifc2x3 #3283

In ifc2x3 IfcProject is not IfcContext because there is no IfcContext in ifc2x3 and it was causing the error below on .ifc import with filtered spatial elements.
Also added small refactor

Traceback:
Error: Python: Traceback (most recent call last):
  File "\blenderbim\bim\module\project\operator.py", line 595, in execute
    ifc_importer.execute()
  File "\blenderbim\bim\import_ifc.py", line 253, in execute
    self.create_spatial_elements()
  File "\blenderbim\bim\import_ifc.py", line 688, in create_spatial_elements
    self.create_generic_elements(self.spatial_elements)
  File "\blenderbim\bim\import_ifc.py", line 698, in create_generic_elements
    products = self.create_products(elements)
  File "\blenderbim\bim\import_ifc.py", line 717, in create_products
    iterator = ifcopenshell.geom.iterator(settings, self.file, multiprocessing.cpu_count(), include=products)
  File "\blenderbim\libs\site\packages\ifcopenshell\geom\main.py", line 99, in __init__
    raise ValueError("include and exclude need to be an aggregate of IfcProduct?")
ValueError: include and exclude need to be an aggregate of IfcProduct?

src/blenderbim/blenderbim/bim/import_ifc.py

@@ -361,7 +361,7 @@ class IfcImporter:
             while True:
                 results.add(spatial_element)
                 spatial_element = ifcopenshell.util.element.get_aggregate(spatial_element)
-                if not spatial_element or spatial_element.is_a("IfcContext"):
+                if not spatial_element or spatial_element.is_a() in ("IfcContext", "IfcProject"):
                     break
         return results
 
@@ -1342,14 +1342,11 @@ class IfcImporter:
         obj.BIMObjectProperties.collection = self.project["blender"]
 
     def create_collections(self):
-        if self.ifc_import_settings.collection_mode == "DECOMPOSITION":
-            self.create_decomposition_collections()
-        elif self.ifc_import_settings.collection_mode == "SPATIAL_DECOMPOSITION":
-            self.create_spatial_decomposition_collections()
-
-    def create_decomposition_collections(self):
         self.create_spatial_decomposition_collections()
-        self.create_aggregate_collections()
+        if self.ifc_import_settings.collection_mode == "DECOMPOSITION":
+            self.create_aggregate_collections()
+        elif self.ifc_import_settings.collection_mode == "SPATIAL_DECOMPOSITION":
+            pass
 
     def create_spatial_decomposition_collections(self):
         for rel_aggregate in self.project["ifc"].IsDecomposedBy or []: