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/.eslintrc.js

@@ -0,0 +1,9 @@
+module.exports = {
+  settings: {
+    "import/resolver": {
+      typescript: {
+        project: __dirname,
+      },
+    },
+  },
+}