[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/onionstudios.py

@@ -1,5 +1,3 @@
-import re
-
 from .common import InfoExtractor
 from ..compat import compat_str
 from ..utils import js_to_json
@@ -7,6 +5,7 @@ from ..utils import js_to_json
 
 class OnionStudiosIE(InfoExtractor):
     _VALID_URL = r'https?://(?:www\.)?onionstudios\.com/(?:video(?:s/[^/]+-|/)|embed\?.*\bid=)(?P<id>\d+)(?!-)'
+    _EMBED_REGEX = [r'(?s)<(?:iframe|bulbs-video)[^>]+?src=(["\'])(?P<url>(?:https?:)?//(?:www\.)?onionstudios\.com/(?:embed.+?|video/\d+\.json))\1']
 
     _TESTS = [{
         'url': 'http://www.onionstudios.com/videos/hannibal-charges-forward-stops-for-a-cocktail-2937',
@@ -29,13 +28,6 @@ class OnionStudiosIE(InfoExtractor):
         'only_matching': True,
     }]
 
-    @staticmethod
-    def _extract_url(webpage):
-        mobj = re.search(
-            r'(?s)<(?:iframe|bulbs-video)[^>]+?src=(["\'])(?P<url>(?:https?:)?//(?:www\.)?onionstudios\.com/(?:embed.+?|video/\d+\.json))\1', webpage)
-        if mobj:
-            return mobj.group('url')
-
     def _real_extract(self, url):
         video_id = self._match_id(url)