Rename UnitType.name what it is: the variant ID.

This property affects safe compat because the ID is what gets preserved
in the save, but it's unfortunately also used as the display name, which
means changing the display name breaks save compat. It also prevents us
from changing display names without breaking faction definitions.

This is the first step in fixing that. The next is adding a separate
display_name property that can be updated without breaking either of
those.

qt_ui/windows/groundobject/QGroundObjectBuyMenu.py

@@ -76,7 +76,7 @@ class QTgoLayoutGroupRow(QWidget):
         # Add all possible units with the price
         for unit_type in force_group.unit_types_for_group(group):
             self.unit_selector.addItem(
-                f"{unit_type.name} [${unit_type.price}M]",
+                f"{unit_type.variant_id} [${unit_type.price}M]",
                 userData=(unit_type.dcs_unit_type, unit_type.price),
             )
         # Add all possible statics with price = 0