[5.x] Add fullyQualifiedHandle method to Blueprint (#11096)

src/Fields/Blueprint.php

@@ -71,6 +71,19 @@ public function namespace(): ?string
         return $this->namespace;
     }
 
+    public function fullyQualifiedHandle(): string
+    {
+        $handle = $this->handle();
+
+        if ($this->namespace()) {
+            $handle = $this->isNamespaced()
+                ? $this->namespace().'::'.$handle
+                : $this->namespace().'.'.$handle;
+        }
+
+        return $handle;
+    }
+
     public function setOrder($order)
     {
         if (! is_null($order)) {