The Pinot UI should distinguish between a server being up and being healthy

[jadami10]

Today, server status Alive just means it has a liveinstance and is connected to the cluster. We should incorporate something like /health or shutdownInProgress into the UI status so it's clearer what the real state of the server is.

[Akanksha-kedia]

@jadami10 please assign to me i want to work .

[Akanksha-kedia]

@Jackie-Jiang please assign i want to work as my first pr.