[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/__init__.py

@@ -1,31 +1,9 @@
-from pathlib import Path
-import logging
+from redbot.core import commands
 
 from .audio import Audio
-from .manager import start_lavalink_server, maybe_download_lavalink
-from redbot.core import commands
-from redbot.core.data_manager import cog_data_path
-import redbot.core
-
-log = logging.getLogger("red.audio")
-
-LAVALINK_DOWNLOAD_URL = (
-    "https://github.com/Cog-Creators/Red-DiscordBot/releases/download/{}/Lavalink.jar"
-).format(redbot.core.__version__)
-
-LAVALINK_DOWNLOAD_DIR = cog_data_path(raw_name="Audio")
-LAVALINK_JAR_FILE = LAVALINK_DOWNLOAD_DIR / "Lavalink.jar"
-
-APP_YML_FILE = LAVALINK_DOWNLOAD_DIR / "application.yml"
-BUNDLED_APP_YML_FILE = Path(__file__).parent / "data/application.yml"
 
 
 async def setup(bot: commands.Bot):
     cog = Audio(bot)
-    if not await cog.config.use_external_lavalink():
-        await maybe_download_lavalink(bot.loop, cog)
-        await start_lavalink_server(bot.loop)
-
     await cog.initialize()
-
     bot.add_cog(cog)