feat(sidekick): Inject InstrumentationClientInfo for tracing (#2252)

- Add static INSTRUMENTATION_CLIENT_INFO to lib.rs.mustache.
- Use INSTRUMENTATION_CLIENT_INFO in transport.rs.mustache if tracing is
enabled.

For #2212 see also
googleapis/google-cloud-rust#3347 and
googleapis/google-cloud-rust#3376

Author: westarle

internal/sidekick/internal/rust/templates/crate/src/lib.rs.mustache

@@ -119,6 +119,15 @@ pub(crate) mod info {
             ac.rest_header_value()
         };
     }
+{{#Codec.DetailedTracingAttributes}}
+    pub(crate) static INSTRUMENTATION_CLIENT_INFO: gaxi::options::InstrumentationClientInfo = gaxi::options::InstrumentationClientInfo {
+        service_name: "{{Name}}",
+        client_version: VERSION,
+        client_artifact: NAME,
+        default_host: "{{Codec.DefaultHostShort}}",
+        ..Default::default()
+    };
+{{/Codec.DetailedTracingAttributes}}
 }
 
 {{/Codec.HasServices}}

internal/sidekick/internal/rust/templates/crate/src/transport.rs.mustache

@@ -53,8 +53,20 @@ impl std::fmt::Debug for {{Codec.Name}} {
 {{/Codec.PerServiceFeatures}}
 impl {{Codec.Name}} {
     pub async fn new(config: gaxi::options::ClientConfig) -> gax::client_builder::Result<Self> {
+        {{#Codec.DetailedTracingAttributes}}
+        let tracing_is_enabled = gaxi::options::tracing_enabled(&config);
+        let inner = gaxi::http::ReqwestClient::new(config, crate::DEFAULT_HOST).await?;
+        let inner = if tracing_is_enabled {
+            inner.with_instrumentation(Some(crate::info::INSTRUMENTATION_CLIENT_INFO))
+        } else {
+            inner
+        };
+        Ok(Self { inner })
+        {{/Codec.DetailedTracingAttributes}}
+        {{^Codec.DetailedTracingAttributes}}
         let inner = gaxi::http::ReqwestClient::new(config, crate::DEFAULT_HOST).await?;
         Ok(Self { inner })
+        {{/Codec.DetailedTracingAttributes}}
     }
 }