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/src/index.ts

@@ -0,0 +1,52 @@
+import * as cs from "code-server"
+import * as fspath from "path"
+
+export const plugin: cs.Plugin = {
+  displayName: "Test Plugin",
+  routerPath: "/test-plugin",
+  homepageURL: "https://example.com",
+  description: "Plugin used in code-server tests.",
+
+  init(config) {
+    config.logger.debug("test-plugin loaded!")
+  },
+
+  router() {
+    const r = cs.express.Router()
+    r.get("/test-app", (_, res) => {
+      res.sendFile(fspath.resolve(__dirname, "../public/index.html"))
+    })
+    r.get("/goland/icon.svg", (_, res) => {
+      res.sendFile(fspath.resolve(__dirname, "../public/icon.svg"))
+    })
+    r.get("/error", () => {
+      throw new cs.HttpError("error", cs.HttpCode.LargePayload)
+    })
+    return r
+  },
+
+  wsRouter() {
+    const wr = cs.WsRouter()
+    wr.ws("/test-app", (req) => {
+      cs.wss.handleUpgrade(req, req.ws, req.head, (ws) => {
+        req.ws.resume()
+        ws.send("hello")
+      })
+    })
+    return wr
+  },
+
+  applications() {
+    return [
+      {
+        name: "Test App",
+        version: "4.0.1",
+        iconPath: "/icon.svg",
+        path: "/test-app",
+
+        description: "This app does XYZ.",
+        homepageURL: "https://example.com",
+      },
+    ]
+  },
+}