Migrate server to ESM

Sorry for the very big commit that may lead to git log issues and merge
conflicts, but it's a major step forward:

 * Server can be faster at startup because imports() are async and we can
   easily lazy import big modules
 * Angular doesn't seem to support ES import (with .js extension), so we
   had to correctly organize peertube into a monorepo:
    * Use yarn workspace feature
    * Use typescript reference projects for dependencies
    * Shared projects have been moved into "packages", each one is now a
      node module (with a dedicated package.json/tsconfig.json)
    * server/tools have been moved into apps/ and is now a dedicated app
      bundled and published on NPM so users don't have to build peertube
      cli tools manually
    * server/tests have been moved into packages/ so we don't compile
      them every time we want to run the server
 * Use isolatedModule option:
   * Had to move from const enum to const
     (https://www.typescriptlang.org/docs/handbook/enums.html#objects-vs-enums)
   * Had to explictely specify "type" imports when used in decorators
 * Prefer tsx (that uses esbuild under the hood) instead of ts-node to
   load typescript files (tests with mocha or scripts):
     * To reduce test complexity as esbuild doesn't support decorator
       metadata, we only test server files that do not import server
       models
     * We still build tests files into js files for a faster CI
 * Remove unmaintained peertube CLI import script
 * Removed some barrels to speed up execution (less imports)

server/tsconfig.json

@@ -1,13 +1,22 @@
 {
   "extends": "../tsconfig.base.json",
   "compilerOptions": {
-    "outDir": "../dist/server"
+    "outDir": "../dist",
+    "baseUrl": "../",
+    "rootDir": ".",
+    "tsBuildInfoFile": "../dist/.tsbuildinfo",
+    "paths": {
+      "@server/*": [ "server/server/*" ]
+    }
   },
   "references": [
-    { "path": "../shared" }
+    { "path": "../packages/core-utils" },
+    { "path": "../packages/ffmpeg" },
+    { "path": "../packages/models" },
+    { "path": "../packages/node-utils" },
+    { "path": "../packages/typescript-utils" }
   ],
-  "exclude": [
-    "tools/",
-    "tests/fixtures"
+  "include": [
+    "./**/*.ts"
   ]
 }