Separate HLS audio and video streams

Allows:
  * The HLS player to propose an "Audio only" resolution
  * The live to output an "Audio only" resolution
  * The live to ingest and output an "Audio only" stream

 This feature is under a config for VOD videos and is enabled by default for lives

 In the future we can imagine:
  * To propose multiple audio streams for a specific video
  * To ingest an audio only VOD and just output an audio only "video"
    (the player would play the audio file and PeerTube would not
    generate additional resolutions)

This commit introduce a new way to download videos:
 * Add "/download/videos/generate/:videoId" endpoint where PeerTube can
   mux an audio only and a video only file to a mp4 container
 * The download client modal introduces a new default panel where the
   user can choose resolutions it wants to download

packages/models/src/server/custom-config.model.ts

@@ -2,6 +2,7 @@ import { NSFWPolicyType } from '../videos/nsfw-policy.type.js'
 import { BroadcastMessageLevel } from './broadcast-message-level.type.js'
 
 export type ConfigResolutions = {
+  '0p': boolean
   '144p': boolean
   '240p': boolean
   '360p': boolean
@@ -133,7 +134,7 @@ export interface CustomConfig {
 
     profile: string
 
-    resolutions: ConfigResolutions & { '0p': boolean }
+    resolutions: ConfigResolutions
 
     alwaysTranscodeOriginalResolution: boolean
 
@@ -143,6 +144,7 @@ export interface CustomConfig {
 
     hls: {
       enabled: boolean
+      splitAudioAndVideo: boolean
     }
   }