chore: Move tracing decorators into the codebase (#4623)

* Vendorize tracing, finally fix service name issues

* Upgrade datadaog-metrics, rename decorators -> tracing

* lint

server/__mocks__/dd-trace.ts

@@ -0,0 +1,39 @@
+/* eslint-disable @typescript-eslint/explicit-function-return-type */
+import { Tracer } from "dd-trace";
+
+// eslint-disable-next-line @typescript-eslint/no-empty-function
+const emptyFn = function () {};
+
+const callableHandlers = {
+  get<T, P extends keyof T>(_target: T, _prop: P, _receiver: any): T[P] {
+    const newMock = new Proxy(emptyFn, callableHandlers);
+    return (newMock as any) as T[P];
+  },
+
+  apply<T extends (...args: any) => any, A extends Parameters<T>>(
+    _target: T,
+    _thisArg: any,
+    _args: A
+  ): ReturnType<T> {
+    const newMock = new Proxy(emptyFn, callableHandlers);
+    return (newMock as any) as ReturnType<T>;
+  },
+};
+
+const callableMock = new Proxy(emptyFn, callableHandlers);
+
+type MockTracer = Tracer & { isMock?: boolean };
+
+export const mockTracer = new Proxy({} as MockTracer, {
+  get<K extends keyof MockTracer>(_target: Tracer, key: K) {
+    if (key === "isMock") {
+      return true;
+    }
+
+    if (key === "wrap") {
+      return (_: any, f: any) => f;
+    }
+
+    return callableMock;
+  },
+});