[extractors] Use new framework for existing embeds (#4307)

`Brightcove` is difficult to migrate because it's subclasses may depend
on the signature of the current functions. So it is left as-is for now

Note: Tests have not been migrated

yt_dlp/extractor/jwplatform.py

@@ -22,13 +22,8 @@ class JWPlatformIE(InfoExtractor):
         'only_matching': True,
     }]
 
-    @staticmethod
-    def _extract_url(webpage):
-        urls = JWPlatformIE._extract_urls(webpage)
-        return urls[0] if urls else None
-
-    @staticmethod
-    def _extract_urls(webpage):
+    @classmethod
+    def _extract_embed_urls(cls, url, webpage):
         for tag, key in ((r'(?:script|iframe)', 'src'), ('input', 'value')):
             # <input value=URL> is used by hyland.com
             # if we find <iframe>, dont look for <input>