[extractor] Add _perform_login function (#2943)

* Adds new functions `_initialize_pre_login` and `_perform_login` as part of the extractor API
* Adds `ie.supports_login` to the public API

yt_dlp/extractor/roosterteeth.py

@@ -21,10 +21,7 @@ class RoosterTeethBaseIE(InfoExtractor):
     _API_BASE = 'https://svod-be.roosterteeth.com'
     _API_BASE_URL = f'{_API_BASE}/api/v1'
 
-    def _login(self):
-        username, password = self._get_login_info()
-        if username is None:
-            return
+    def _perform_login(self, username, password):
         if self._get_cookies(self._API_BASE_URL).get('rt_access_token'):
             return
 
@@ -47,9 +44,6 @@ class RoosterTeethBaseIE(InfoExtractor):
                         msg += ': ' + error
             self.report_warning(msg)
 
-    def _real_initialize(self):
-        self._login()
-
     def _extract_video_info(self, data):
         thumbnails = []
         for image in traverse_obj(data, ('included', 'images')):