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/test_node_es_modules.py

@@ -0,0 +1,50 @@
+import pytest
+
+from distutils.version import LooseVersion
+from unit.applications.lang.node import TestApplicationNode
+from unit.applications.websockets import TestApplicationWebsocket
+
+
+class TestNodeESModules(TestApplicationNode):
+    prerequisites = {
+        'modules': {
+            'node': lambda v:  LooseVersion(v) >= LooseVersion("14.16.0")
+        }
+    }
+
+    es_modules = True
+    ws = TestApplicationWebsocket()
+
+    def assert_basic_application(self):
+        resp = self.get()
+        assert resp['headers']['Content-Type'] == 'text/plain', 'basic header'
+        assert resp['body'] == 'Hello World\n', 'basic body'
+
+    def test_node_es_modules_require_shim_http(self):
+        self.load('require_shim/es_modules_http', name="app.mjs")
+
+        self.assert_basic_application()
+
+    def test_node_es_modules_require_shim_http_indirect(self):
+        self.load('require_shim/es_modules_http_indirect', name="app.js")
+
+        self.assert_basic_application()
+
+    def test_node_es_modules_require_shim_websockets(self):
+        self.load('require_shim/es_modules_websocket', name="app.mjs")
+
+        message = 'blah'
+
+        _, sock, _ = self.ws.upgrade()
+
+        self.ws.frame_write(sock, self.ws.OP_TEXT, message)
+        frame = self.ws.frame_read(sock)
+
+        assert message == frame['data'].decode('utf-8'), 'mirror'
+
+        self.ws.frame_write(sock, self.ws.OP_TEXT, message)
+        frame = self.ws.frame_read(sock)
+
+        assert message == frame['data'].decode('utf-8'), 'mirror 2'
+
+        sock.close()