feat: make traceContext accessible (#1696)

* feat: make traceContext accessible

* chore: remove traceContext export in v1

Author: CorieW

src/common/trace.ts

@@ -1,6 +1,5 @@
 import { AsyncLocalStorage } from "async_hooks";
 
-/* @internal */
 export const traceContext = new AsyncLocalStorage<TraceContext>();
 
 export interface TraceContext {

src/v2/index.ts

@@ -70,6 +70,7 @@ export {
 
 export { CloudFunction, CloudEvent, ParamsOf, onInit } from "./core";
 export { Change } from "../common/change";
+export { traceContext } from "../common/trace";
 // NOTE: Equivalent to `export * as params from "../params"` but api-extractor doesn't support that syntax.
 import * as params from "../params";
 export { params };