Revert "refactor: move test-plugin to integration suite"

This reverts commit bc02005dc0.

I couldn't get past some GLIBC errors in CI so moving back to unit
tests.

test/unit/node/test-plugin/package.json

@@ -0,0 +1,16 @@
+{
+  "private": true,
+  "name": "test-plugin",
+  "version": "1.0.0",
+  "engines": {
+    "code-server": "^4.7.0"
+  },
+  "main": "out/index.js",
+  "devDependencies": {
+    "@types/express": "^4.17.8",
+    "typescript": "^4.0.5"
+  },
+  "scripts": {
+    "build": "tsc"
+  }
+}