Add id3v2 export to HLS output.

[toots]

This PR implements support for ID3 metadata for HLS output.

From the doc:

Metadata

HLS outputs supports metadata in two ways:

• Through a timed_id3 metadata logical stream with the mpegts format.
• Through regular ID3 frames, as requested by the HLS specifications for adts, mp3, ac3 and eac3 formats.
• There is currently no support for in-stream metadata for the mp4 format.

Metadata parameters are passed through the record methods of the streams' encoders. Here's an example

output.file.hls(
  "/path/to/directory",
  [
   ("aac",
      %ffmpeg(format="adts", %audio(codec="aac")).{
        id3_version = 3
       }),
   ("ts-with-meta",
      %ffmpeg(format="mpegts", %audio(codec="aac")).{
        id3_version = 4
     }),
   ("ts",
      %ffmpeg(format="mpegts", %audio(codec="aac")).{
        id3 = false
      }),
   ("mp3",
      %ffmpeg(format="mp3", %audio(codec="libmp3lame")).{
        replay_id3 = false
      })
  ],
  source
)

Parameters are:

• id3: Set to false to deactivate metadata on the streams. Defaults to true.
• id3_version: Set the id3v2 version used to export metadata
• replay_id3: By default, the latest metadata is inserted at the beginning of each segment to make sure new listeners always get the latest metadata. Set to false to disable it.

Metadata for these formats are activated by default. If you are experiencing any issues with them, you can disable them by setting id3 to false.

Fixes: #3153

[Russsgithub]

This is great. Thanks