chore: Remove state engine (#5752)

The state engine mechanism, designed for the player class, was
over-engineered. The structure of the class makes debugging player
errors unnecessarily annoying, by obfuscating the code-path the error
followed, and in general
has created a significant amount of technical debt.
This changes the player to use an async-await setup for the top-level
operations, laying things out much more cleanly
and linearly.

---------

Co-authored-by: Álvaro Velad Galván <ladvan91@hotmail.com>

docs/tutorials/basic-usage.md

@@ -52,7 +52,8 @@ function initApp() {
 async function initPlayer() {
   // Create a Player instance.
   const video = document.getElementById('video');
-  const player = new shaka.Player(video);
+  const player = new shaka.Player();
+  async player.attach(video);
 
   // Attach player to the window to make it easy to access in the JS console.
   window.player = player;