[Audio] Refactor internal Lavalink server management (#2495)

* Refactor internal Lavalink server management

Killing many birds with one stone here.
- Made server manager into class-based API with two public methods: `start()` and `shutdown()`. Must be re-instantiated each time it is restarted.
- Using V3 universal Lavalink.jar hosted on Cog-Creators/Lavalink-Jars repository.
- Uses output of `java -jar Lavalink.jar --version` to check if a new jar needs to be downloaded.
- `ServerManager.start()` won't return until server is ready, i.e. when "Started Launcher in X seconds" message is printed to STDOUT.
- `shlex.quote()` is used so spaces in path to Lavalink.jar don't cause issues.
- Enabling external Lavalink will cause internal server to be terminated.
- Disabling internal Lavalink will no longer reset settings in config - instead, hard-coded values will be used when connecting to an internal server.
- Internal server will now run both WS and REST servers on port 2333, meaning one less port will need to be taken up.
- Now using `asyncio.subprocess` module so waiting on and reading from subprocesses can be done asynchronously.

Signed-off-by: Toby Harradine <tobyharradine@gmail.com>

* Don't use shlex.quote on Windows

Signed-off-by: Toby <tobyharradine@gmail.com>

* Don't use shlex.quote at all

I misread a note in the python docs and assumed it was best to use it. Turns out the note only applies to `asyncio.create_subprocess_shell`.

Signed-off-by: Toby <tobyharradine@gmail.com>

* Missed the port on the rebase

* Ignore invalid architectures and inform users when commands are used.

* Style fix

redbot/cogs/audio/data/application.yml

@@ -1,11 +1,9 @@
 server:
+  host: "localhost"
   port: 2333 # REST server
 lavalink:
   server:
     password: "youshallnotpass"
-    ws:
-      host: "localhost"
-      port: 2332
     sources:
       youtube: true
       bandcamp: true