[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/senategov.py

@@ -49,6 +49,7 @@ _COMMITTEES = {
 class SenateISVPIE(InfoExtractor):
     _IE_NAME = 'senate.gov:isvp'
     _VALID_URL = r'https?://(?:www\.)?senate\.gov/isvp/?\?(?P<qs>.+)'
+    _EMBED_REGEX = [r"<iframe[^>]+src=['\"](?P<url>https?://www\.senate\.gov/isvp/?\?[^'\"]+)['\"]"]
 
     _TESTS = [{
         'url': 'http://www.senate.gov/isvp/?comm=judiciary&type=live&stt=&filename=judiciary031715&auto_play=false&wmode=transparent&poster=http%3A%2F%2Fwww.judiciary.senate.gov%2Fthemes%2Fjudiciary%2Fimages%2Fvideo-poster-flash-fit.png',
@@ -87,14 +88,6 @@ class SenateISVPIE(InfoExtractor):
         'only_matching': True,
     }]
 
-    @staticmethod
-    def _search_iframe_url(webpage):
-        mobj = re.search(
-            r"<iframe[^>]+src=['\"](?P<url>https?://www\.senate\.gov/isvp/?\?[^'\"]+)['\"]",
-            webpage)
-        if mobj:
-            return mobj.group('url')
-
     def _real_extract(self, url):
         url, smuggled_data = unsmuggle_url(url, {})