Node.js: a shim for overriding "http" and "websocket" modules.

Also added stubs for Server.address()
This was done to prevent crashes in some popular frameworks like express

Supports both CommonJS and the new ES Modules system syntax e.g:

app.js:
const http = require('http')

app.mjs:
import http from "http"

Usage on Node 14.16.x and higher:
{
    "type": "external",
    "processes": {"spare": 0},
    "working_directory": '/project',
    "executable": "/usr/bin/env",
    "arguments": [
        "node",
        "--loader",
        "unit-http/require_shim.mjs"
        "--require",
        "unit-http/require_shim",
        "app.js"
    ]
}

Usage on Node 14.15.x and lower:
{
    "type": "external",
    "processes": {"spare": 0},
    "working_directory": '/project',
    "executable": "/usr/bin/env",
    "arguments": [
        "node",
        "--require",
        "unit-http/require_shim",
        "app.js"
    ]
}

test/unit/check/node.py

@@ -1,6 +1,15 @@
 import os
+import subprocess
 
 
 def check_node(current_dir):
-    if os.path.exists(current_dir + '/node/node_modules'):
-        return True
+    if not os.path.exists(current_dir + '/node/node_modules'):
+        return None
+
+    try:
+        v_bytes = subprocess.check_output(['/usr/bin/env', 'node', '-v'])
+
+        return [str(v_bytes, 'utf-8').lstrip('v').rstrip()]
+
+    except subprocess.CalledProcessError:
+        return None