Adapt config tests

Author: anna-git

tracer/test/Datadog.Trace.Tests/Configuration/Telemetry/ConfigurationBuilderTests.cs

@@ -35,7 +35,8 @@ public IConfigurationSource GetSource(IDictionary<string, object> values)
                 var data = new NameValueCollection();
                 foreach (var kvp in values)
                 {
-                    data.Add(kvp.Key, kvp.Value?.ToString());
+                    // use FormattableString.Invariant as europeans might have 1.23.ToString()=1,23 which makes tests fail
+                    data.Add(kvp.Key, kvp.Value is null ? null : FormattableString.Invariant($"{kvp.Value}"));
                 }
 
                 return new NameValueConfigurationSource(data);

tracer/test/Datadog.Trace.Tests/Telemetry/ConfigurationTests.cs

@@ -58,6 +58,8 @@ public class ConfigurationTests
         "DD_INSTRUMENTATION_INSTALL_TIME",
         "DD_INJECTION_ENABLED",
         "DD_INJECT_FORCE",
+        // deprecated alias
+        "DATADOG_TRACE_AGENT_HOSTNAME_OPTIMIZED"
     };
 
     // These are the keys that are used in the integration registry which are _not_ sent to telemetry, so we can ignore them