Support distributed tracing

[ikhoon]

If distributed tracing is supported by a Central Dogma server, users can easily find a performance bottleneck in their request paths and visualize the dependencies of the Central Dogma server.

We will define a configuration for distributedTracing and make the server report tracing information based on that.

{ 
  "distributedTracing": {
    "collectorUrl": "http://127.0.0.1:.../api/../spans",
    "serviceName": "CentralDogma",
    "samplingRate": "0.01",
    ...
  }
}

A builder API can be also used to configure distributed tracing for both a server and a client.

[trustin]

We might want to wait for Micrometer Tracing integration in Armeria first though