Flatten lib namespace

Move all functions and classes currently available through lib/name and
libName to be under a single flat namespace in lib.  This make
reorganising the lib namespace much simpler as the location of symbols
can move without breaking the consumers of lib.

The multi-entrypoint design was already problematic for the web plugin
system which couldn't effectively use it due to how webpack's shared
module system is awkward to set up with multiple entrypoints per package.

test/controller/HttpCloser.js

@@ -7,7 +7,6 @@ const util = require("util");
 
 const phin = require("phin");
 
-const { wait } = require("@clusterio/lib/helpers");
 const HttpCloser = require("@clusterio/controller/src/HttpCloser");
 
 // Time to wait during async operations to ensure they happened in order.

test/controller/routes.js

@@ -6,7 +6,7 @@ const jwt = require("jsonwebtoken");
 const http = require("http");
 const phin = require("phin");
 
-const { wait } = require("@clusterio/lib/helpers");
+const { wait } = require("@clusterio/lib");
 const routes = require("@clusterio/controller/src/routes");
 const mock = require("../mock");