add Cluster, region and datacenter to rust tracing scuba

Summary:
**NOTE**: Please reviewers not sure if adding those fields here is proper. Per what I understand this will not impact `with_common_fields` function. Not sure if I should also add this to this other [builder](https://www.internalfb.com/code/fbsource/[370994e07362]/fbcode/common/rust/scuba/src/builder.rs?lines=182)

This diffs adds Cluster, Region and Datacenter to the possible common fields to log

Note those fields are part of the TW job handle, but sometimes we want to log them individually.

Reviewed By: emersonford

Differential Revision: D50523275

fbshipit-source-id: 2eab3111aab6dfd2bb346772219204ac5461aedd

shed/scuba_sample/src/builder.rs

@@ -264,10 +264,16 @@ pub enum ServerData {
     Hostname,
     /// Hostname scheme of the server
     HostnameScheme,
+    /// Datacenter Region
+    Region,
+    /// Datacenter prefix
+    Datacenter,
     /// Tier of the service
     Tier,
     /// Tupperware TaskId of the service
     TaskId,
+    /// Tupperware cluster name
+    Cluster,
     /// Tupperware CanaryId of the service
     CanaryId,
     /// Tupperware JobHandle of the service
@@ -294,7 +300,10 @@ impl ServerData {
         match self {
             ServerData::Hostname => "server_hostname",
             ServerData::HostnameScheme => "server_hostname_scheme",
+            ServerData::Region => "region",
+            ServerData::Datacenter => "datacenter",
             ServerData::Tier => "server_tier",
+            ServerData::Cluster => "tw_cluster",
             ServerData::TaskId => "tw_task_id",
             ServerData::CanaryId => "tw_canary_id",
             ServerData::JobHandle => "tw_handle",