Regression: hand interaction profile is not available

When we removed the KHR simple profile in c3b539a we also did
delete the code that was handling profiles with no specific
device. That was a mistake because that's precisely the case
of generic profiles like hand interaction.

Restored the code adding those profiles to the list of available
mappings.

app/src/openxr/cpp/OpenXRInputSource.cpp

@@ -77,10 +77,14 @@ XrResult OpenXRInputSource::Initialize()
         systemDoF = DoF::IS_6DOF;
     }
     for (auto& mapping: OpenXRInputMappings) {
-      if (mDeviceType != mapping.controllerType)
-        continue;
-
-      if (systemDoF != mapping.systemDoF)
+      // Always populate default/fall-back profiles
+      if (mapping.controllerType == device::UnknownType) {
+          mMappings.push_back(mapping);
+          // Use the system's deviceType instead to ensure we get a valid VRController on WebXR sessions
+          mMappings.back().controllerType = mDeviceType;
+          continue;
+      }
+      if ((mDeviceType != mapping.controllerType) || (systemDoF != mapping.systemDoF))
           continue;
       mMappings.push_back(mapping);
     }