[multistage] Revisit Stage Level Unique RequestId

Looks like we are making request-ids unique at stage level for the leaf stage execution.

This doesn't fit neatly with the concept of request-id because we'd want a single request-id for tracing. Can someone confirm if and what the plan is to fix this?

cc: @walterddr

https://github.com/apache/pinot/blob/04bdb9a39743569aaacfcb07e2cc7eaa08854791/pinot-query-runtime/src/main/java/org/apache/pinot/query/runtime/plan/server/ServerPlanRequestUtils.java#L126C13-L126C13