New feature to manipulate cost item quantities

src/ifcopenshell-python/ifcopenshell/api/cost/remove_cost_item_quantity.py

@@ -0,0 +1,14 @@
+class Usecase:
+    def __init__(self, file, **settings):
+        self.file = file
+        self.settings = {"cost_item": None, "physical_quantity": None}
+        for key, value in settings.items():
+            self.settings[key] = value
+
+    def execute(self):
+        if len(self.file.get_inverse(self.settings["physical_quantity"])) == 1:
+            self.file.remove(self.settings["physical_quantity"])
+            return
+        quantities = list(self.settings["cost_item"].CostQuantities or [])
+        quantities.remove(self.settings["physical_quantity"])
+        self.settings["cost_item"].CostQuantities = quantities