Improve the visibility of barrier collecting

[fuyufjh]

Yesterday I ran into a stuck related to LocalBarrierManager and LocalBarrierWorker, but I failed to get any information inside it. It's like a blackbox at all.

[RPC risingwave-compute-0.risingwave-compute:5688 - 2064]
/stream_service.StreamService/BarrierComplete [3843.568s]
  collect_barrier (epoch 6220276010844160) [!!! 3843.568s]

-- What's happenened inside ??? No actos were blocked at `6220276010844160`...

Since barrier collecting is quite important for streaming, I think we need a way to expose the state inside LocalBarrierWorker, for example, export the current collecting progress.

• Add a InspectState event in LocalBarrierWorker to export the current barrier states
• feat: support inspecting local barrier worker state #16562
• (need-investigation) Export internal state in Meta node's BarrierManager
• Output the results via an API endpoint & risectl command
• (need-investigation) Add await tree dump for LocalBarrierWorker and Uploader