Fix: get_applicable return empty generator (#1390)

`PsetQto.get_applicable` was returning an empty generator when called
multiple times. Combination on lru_cache and generator seems to lead to
this unwanted behavior.
It now returns a list to keep gains of lru_cache performance.

src/ifcopenshell-python/ifcopenshell/util/test_pset.py

@@ -0,0 +1,17 @@
+"""Run this test from src/ifcopenshell-python folder: pytest --durations=0 ifcopenshell/util/test_pset.py"""
+from ifcopenshell.util import pset
+from ifcopenshell import util
+
+
+class TestPsetQto:
+    @classmethod
+    def setup_class(cls):
+        cls.pset_qto = util.pset.PsetQto("IFC4")
+
+    def test_get_applicables(self):
+        for i in range(1000):
+            assert len(self.pset_qto.get_applicable("IfcMaterial")) == 14
+
+    def test_get_applicables_names(self):
+        for i in range(1000):
+            assert len(self.pset_qto.get_applicable_names("IfcMaterial")) == 14