ifc5d: wire up GrossFootprintArea/NetFootprintArea for IfcWall QTO

Root cause: the IfcOpenShell-geometry-engine calculator ruleset
(IFC4QtoBaseQuantities.json and IFC4X3QtoBaseQuantities.json) left
IfcWall's GrossFootprintArea/NetFootprintArea mapped to null, so
these two quantities were silently omitted from Qto_WallBaseQuantities
whenever that ruleset was used. The generic gross_get_footprint_area
and net_get_footprint_area formulas already exist and are already
wired up for IfcSlab in the same files, so this was a missing mapping,
not a missing implementation.

Fixes #7029.

Generated with the assistance of an AI coding tool.

(cherry picked from commit f3cb7aea61)

src/ifc5d/ifc5d/IFC4QtoBaseQuantities.json

@@ -606,13 +606,13 @@
             },
             "IfcWall": {
                 "Qto_WallBaseQuantities": {
-                    "GrossFootprintArea": null,
+                    "GrossFootprintArea": "gross_get_footprint_area",
                     "GrossSideArea": "gross_get_side_area",
                     "GrossVolume": "gross_get_volume",
                     "GrossWeight": "gross_get_weight",
                     "Height": "net_get_z",
                     "Length": "net_get_x",
-                    "NetFootprintArea": null,
+                    "NetFootprintArea": "net_get_footprint_area",
                     "NetSideArea": "net_get_side_area",
                     "NetVolume": "net_get_volume",
                     "NetWeight": "net_get_weight",

src/ifc5d/ifc5d/IFC4X3QtoBaseQuantities.json

@@ -769,13 +769,13 @@
             },
             "IfcWall + IfcWallType": {
                 "Qto_WallBaseQuantities": {
-                    "GrossFootPrintArea": null,
+                    "GrossFootPrintArea": "gross_get_footprint_area",
                     "GrossSideArea": "gross_get_side_area",
                     "GrossVolume": "gross_get_volume",
                     "GrossWeight": "gross_get_weight",
                     "Height": "net_get_z",
                     "Length": "net_get_x",
-                    "NetFootPrintArea": null,
+                    "NetFootPrintArea": "net_get_footprint_area",
                     "NetSideArea": "net_get_side_area",
                     "NetVolume": "net_get_volume",
                     "NetWeight": "net_get_weight",