http: throw if 'host' agent header is not a string value

If the 'host' agent header is an array or other non-string value, throw.

PR-URL: https://github.com/nodejs/node/pull/29568
Fixes: https://github.com/nodejs/node/issues/29408
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>

test/parallel/test-http-client-headers-host-array.js

@@ -0,0 +1,23 @@
+'use strict';
+
+require('../common');
+
+const assert = require('assert');
+const http = require('http');
+
+{
+
+  const options = {
+    port: '80',
+    path: '/',
+    headers: {
+      host: []
+    }
+  };
+
+  assert.throws(() => {
+    http.request(options);
+  }, {
+    code: /ERR_INVALID_ARG_TYPE/
+  }, 'http request should throw when passing array as header host');
+}