fix(barcode-scanner): settle the pending scan() promise on cancel (fix #3560) (#3571)

On Android, cancel() called destroy() first, and destroy() sets
savedInvoke to null, so the savedInvoke?.reject("cancelled") that
follows was a no-op. The pending scan() promise was never settled and
callers awaiting it were stranded, which is especially bad in windowed
mode where the page background stays transparent.

Reject the pending invoke before tearing the camera down, matching the
order the iOS implementation already uses.

plugins/barcode-scanner/android/src/main/java/BarcodeScannerPlugin.kt

@@ -332,8 +332,10 @@ class BarcodeScannerPlugin(private val activity: Activity) : Plugin(activity),
 
     @Command
     fun cancel(invoke: Invoke) {
-        destroy()
+        // Reject the pending scan before destroy() clears savedInvoke, otherwise the
+        // scan() promise is never settled. Mirrors the iOS implementation.
         savedInvoke?.reject("cancelled")
+        destroy()
         invoke.resolve()
     }