[rai] Detect ContentItem in iframe (closes #12652) (#27673)

Co-authored-by: Sergey M. <dstftw@gmail.com>

youtube_dl/extractor/rai.py

@@ -326,6 +326,19 @@ class RaiIE(RaiBaseIE):
         'params': {
             'skip_download': True,
         },
+    }, {
+        # ContentItem in iframe (see #12652)
+        'url': 'http://www.presadiretta.rai.it/dl/portali/site/puntata/ContentItem-3ed19d13-26c2-46ff-a551-b10828262f1b.html',
+        'info_dict': {
+            'id': '1ad6dc64-444a-42a4-9bea-e5419ad2f5fd',
+            'ext': 'mp4',
+            'title': 'Partiti acchiappavoti - Presa diretta del 13/09/2015',
+            'description': 'md5:d291b03407ec505f95f27970c0b025f4',
+            'upload_date': '20150913',
+        },
+        'params': {
+            'skip_download': True,
+        },
     }, {
         # Direct MMS URL
         'url': 'http://www.rai.it/dl/RaiTV/programmi/media/ContentItem-b63a4089-ac28-48cf-bca5-9f5b5bc46df5.html',
@@ -403,7 +416,8 @@ class RaiIE(RaiBaseIE):
                 r'''(?x)
                     (?:
                         (?:initEdizione|drawMediaRaiTV)\(|
-                        <(?:[^>]+\bdata-id|var\s+uniquename)=
+                        <(?:[^>]+\bdata-id|var\s+uniquename)=|
+                        <iframe[^>]+\bsrc=
                     )
                     (["\'])
                     (?:(?!\1).)*\bContentItem-(?P<id>%s)