[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/odnoklassniki.py

@@ -1,5 +1,3 @@
-import re
-
 from .common import InfoExtractor
 from ..compat import (
     compat_etree_fromstring,
@@ -31,6 +29,7 @@ class OdnoklassnikiIE(InfoExtractor):
                     )
                     (?P<id>[\d-]+)
                 '''
+    _EMBED_REGEX = [r'<iframe[^>]+src=(["\'])(?P<url>(?:https?:)?//(?:odnoklassniki|ok)\.ru/videoembed/.+?)\1']
     _TESTS = [{
         'note': 'Coub embedded',
         'url': 'http://ok.ru/video/1484130554189',
@@ -161,13 +160,6 @@ class OdnoklassnikiIE(InfoExtractor):
         'only_matching': True,
     }]
 
-    @staticmethod
-    def _extract_url(webpage):
-        mobj = re.search(
-            r'<iframe[^>]+src=(["\'])(?P<url>(?:https?:)?//(?:odnoklassniki|ok)\.ru/videoembed/.+?)\1', webpage)
-        if mobj:
-            return mobj.group('url')
-
     def _real_extract(self, url):
         try:
             return self._extract_desktop(url)