youtube-dl refactor (#956)

* Consolidated all youtube-dl calls into one function
* Downloads can now be cancelled and better "paused"
* Removed node-youtube-dl dependency
* Added ability to manually check a subscription, and to cancel a subscription check

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Co-authored-by: Dedy Martadinata S <dedyms@proton.me>

backend/utils.js

@@ -241,11 +241,6 @@ exports.addUIDsToCategory = (category, files) => {
     return files_that_match;
 }
 
-exports.getCurrentDownloader = () => {
-    const details_json = fs.readJSONSync(CONSTS.DETAILS_BIN_PATH);
-    return details_json['downloader'];
-}
-
 exports.recFindByExt = async (base, ext, files, result, recursive = true) => {
     files = files || (await fs.readdir(base))
     result = result || []