Make signal callbacks work similar as regular callbacks in JNI (#8048)

**Reason**
- Emitting on the signal generated with bindgen didn't work while
scheduling with the scheduler from C++. It happened that on activation
we tried to findClass using the `attachedEnv` which had different
classLoader due to the fact it was called from C++ context and callback
class couldn't be resolved. Which menat that if a schedule emission from
different thread JNI silently crashed

**Content**
- Make signal to generate callback the similar way we generate the
callbacks for `callback` type, meaning that instead of retrieving the
callback class dynamically when the callback invoked we store the
callback objects class as static ref
- We statically store this class metadata only one and it's unique per
type not per instance, so it's accepatable overhead, following the
regular callbacks patter

cc @mapbox/nav-core-sdk
cc @mapbox/core-sdk
cc @mapbox/gl-native
cc @mapbox/maps-android

GitOrigin-RevId: b8eefe5c0beec056dd3474c628986ff4803803c6

Author: aleksproger

app/src/main/java/com/mapbox/maps/testapp/examples/IndoorExampleActivity.kt

@@ -30,31 +30,30 @@ class IndoorExampleActivity : AppCompatActivity() {
         zoom(ZOOM)
         bearing(BEARING)
         pitch(PITCH)
-      }
+      },
+      styleUri = STYLE_URI
     )
 
     val mapView = MapView(this, mapInitOptions)
     setContentView(mapView)
     val mapboxMap = mapView.mapboxMap
 
     mapboxMap.getStyle {
-      // Select a specific floor (this ID should match a floor in your indoor data)
-      // Example floor ID - replace with actual floor ID from your indoor data
-      mapboxMap.indoor.selectFloor(FLOOR_ID)
-
-      // Listen to indoor state updates
       mapboxMap.indoor.setOnIndoorUpdatedCallback(object : IndoorManager.OnIndoorUpdatedCallback {
         override fun onOnIndoorUpdated(onIndoorUpdated: IndoorState) {
-          logD(TAG, "Indoor state updated: $onIndoorUpdated")
-          logD(TAG, "Available floors: ${onIndoorUpdated.floors}")
-          logD(TAG, "Selected floor: ${onIndoorUpdated.selectedFloorId}")
+          logD(TAG, "Indoor_Subscriber_0: Indoor state updated: $onIndoorUpdated")
+          logD(TAG, "Indoor_Subscriber_0: Selected floor: ${onIndoorUpdated.selectedFloorId}")
         }
       })
+
+      logD(TAG, "Indoor: selectFloor: $FLOOR_ID")
+      mapboxMap.indoor.selectFloor(FLOOR_ID)
     }
   }
 
   companion object {
     private const val TAG = "IndoorExampleActivity"
+    private const val STYLE_URI = "mapbox://styles/mapbox/streets-v12"
 
     // JFK Airport coordinates
     private const val LATITUDE = 40.6441