feat(server): use x-cloud-trace-context instead of x-rpc-trace-id (#10068)

x-cloud-trace-context will be overwritten by lb,
and cannot be fake from internet access request

![image.png](https://graphite-user-uploaded-assets-prod.s3.amazonaws.com/hTwOityLamd4hitrae7M/6d3c47c1-ac9e-4bc9-a7f1-2be8f56dbf69.png)

packages/backend/server/src/core/doc/reader.ts

@@ -46,7 +46,7 @@ export class RpcDocReader extends DatabaseDocReader {
       const res = await fetch(url, {
         headers: {
           'x-access-token': this.crypto.sign(docId),
-          'x-rpc-trace-id': this.cls.getId(),
+          'x-cloud-trace-context': this.cls.getId(),
         },
       });
       if (!res.ok) {