add server uuid in /proton/info api

[qijun-niu-timeplus]

PR checklist:

• Did you run ClangFormat ?
• Did you separate headers to a different section in existing community code base ?
• Did you surround proton: starts/ends for new code in existing community code base ?

Please write user-readable short description of the changes:

➜  ~ curl http://localhost:8123/proton/info | jq
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   232    0   232    0     0  29000      0 --:--:-- --:--:-- --:--:-- 29000
{
  "build": {
    "commit_sha": "c81b845b",
    "edition": "oss",
    "name": "proton",
    "time": "2024-05-16T03:19:49Z",
    "version": "v1.5.8"
  },
  "server": {
    "memory_amount": 33324388352,
    "num_of_physical_cpu_cores": 20,
    "uuid": "bdb623fe-0973-4083-8f83-7fca70a38f59"
  }
}

[chenziliang]

don't need to set unknown, Nil format is good to go