Improve --clean-infojson

It should not removes fields that may be needed for `--load-infojson`.
Eg: `_ffmpeg_args`, `_has_drm`

yt_dlp/extractor/common.py

@@ -208,8 +208,10 @@ class InfoExtractor:
                     * no_resume  The server does not support resuming the
                                  (HTTP or RTMP) download. Boolean.
                     * has_drm    The format has DRM and cannot be downloaded. Boolean
-                    * downloader_options  A dictionary of downloader options as
-                                 described in FileDownloader (For internal use only)
+                    * downloader_options  A dictionary of downloader options
+                                 (For internal use only)
+                                 * http_chunk_size Chunk size for HTTP downloads
+                                 * ffmpeg_args     Extra arguments for ffmpeg downloader
                     RTMP formats can also have the additional fields: page_url,
                     app, play_path, tc_url, flash_version, rtmp_live, rtmp_conn,
                     rtmp_protocol, rtmp_real_time

yt_dlp/extractor/nbc.py

@@ -579,7 +579,7 @@ class NBCOlympicsStreamIE(AdobePassIE):
         for f in formats:
             # -http_seekable requires ffmpeg 4.3+ but it doesnt seem possible to
             # download with ffmpeg without this option
-            f['_ffmpeg_args'] = ['-seekable', '0', '-http_seekable', '0', '-icy', '0']
+            f['downloader_options'] = {'ffmpeg_args': ['-seekable', '0', '-http_seekable', '0', '-icy', '0']}
         self._sort_formats(formats)
 
         return {

yt_dlp/extractor/radiko.py

@@ -125,7 +125,7 @@ class RadikoBaseIE(InfoExtractor):
                     # Prioritize live radio vs playback based on extractor
                     sf['preference'] = 100 if is_onair else -100
                 if not is_onair and url_attrib['timefree'] == '1' and time_to_skip:
-                    sf['_ffmpeg_args'] = ['-ss', time_to_skip]
+                    sf['downloader_options'] = {'ffmpeg_args': ['-ss', time_to_skip]}
             formats.extend(subformats)
 
         self._sort_formats(formats)

yt_dlp/extractor/turner.py

@@ -141,7 +141,7 @@ class TurnerBaseIE(AdobePassIE):
                     m3u8_id=format_id or 'hls', fatal=False)
                 if '/secure/' in video_url and '?hdnea=' in video_url:
                     for f in m3u8_formats:
-                        f['_ffmpeg_args'] = ['-seekable', '0']
+                        f['downloader_options'] = {'ffmpeg_args': ['-seekable', '0']}
                 formats.extend(m3u8_formats)
             elif ext == 'f4m':
                 formats.extend(self._extract_f4m_formats(