[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/panopto.py

@@ -1,4 +1,3 @@
-import re
 import calendar
 import json
 import functools
@@ -73,15 +72,10 @@ class PanoptoBaseIE(InfoExtractor):
     def _parse_fragment(url):
         return {k: json.loads(v[0]) for k, v in compat_urlparse.parse_qs(compat_urllib_parse_urlparse(url).fragment).items()}
 
-    @staticmethod
-    def _extract_urls(webpage):
-        return [m.group('url') for m in re.finditer(
-            r'<iframe[^>]+src=["\'](?P<url>%s/Pages/(Viewer|Embed|Sessions/List)\.aspx[^"\']+)' % PanoptoIE.BASE_URL_RE,
-            webpage)]
-
 
 class PanoptoIE(PanoptoBaseIE):
     _VALID_URL = PanoptoBaseIE.BASE_URL_RE + r'/Pages/(Viewer|Embed)\.aspx.*(?:\?|&)id=(?P<id>[a-f0-9-]+)'
+    _EMBED_REGEX = [rf'<iframe[^>]+src=["\'](?P<url>{PanoptoBaseIE.BASE_URL_RE}/Pages/(Viewer|Embed|Sessions/List)\.aspx[^"\']+)']
     _TESTS = [
         {
             'url': 'https://demo.hosted.panopto.com/Panopto/Pages/Viewer.aspx?id=26b3ae9e-4a48-4dcc-96ba-0befba08a0fb',