[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/piksel.py

@@ -30,6 +30,7 @@ class PikselIE(InfoExtractor):
             )\.jp|
             vidego\.baltimorecity\.gov
         )/v/(?:refid/(?P<refid>[^/]+)/prefid/)?(?P<id>[\w-]+)'''
+    _EMBED_REGEX = [r'<iframe[^>]+src=["\'](?P<url>(?:https?:)?//player\.piksel\.com/v/[a-z0-9]+)']
     _TESTS = [
         {
             'url': 'http://player.piksel.com/v/ums2867l',
@@ -62,14 +63,6 @@ class PikselIE(InfoExtractor):
         }
     ]
 
-    @staticmethod
-    def _extract_url(webpage):
-        mobj = re.search(
-            r'<iframe[^>]+src=["\'](?P<url>(?:https?:)?//player\.piksel\.com/v/[a-z0-9]+)',
-            webpage)
-        if mobj:
-            return mobj.group('url')
-
     def _call_api(self, app_token, resource, display_id, query, fatal=True):
         response = (self._download_json(
             'http://player.piksel.com/ws/ws_%s/api/%s/mode/json/apiv/5' % (resource, app_token),