[ASM]Fix appsec waf benchmark for real (#6329)

## Summary of changes

Don't throw when creating a trace context and an empty datadog tracer

## Reason for change

It [was throwing](https://datadoghq.atlassian.net/browse/APMAPI-893)
when creating the context.

## Implementation details

## Test coverage

## Other details
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Author: anna-git

tracer/test/benchmarks/Benchmarks.Trace/Asm/EmptyDatadogTracer.cs

@@ -19,15 +19,15 @@ public class EmptyDatadogTracer : IDatadogTracer
     {
         public string DefaultServiceName => "My Service Name";
 
-        public ImmutableTracerSettings Settings => throw new NotImplementedException();
+        public ImmutableTracerSettings Settings => new(new NullConfigurationSource());
 
-        IGitMetadataTagsProvider IDatadogTracer.GitMetadataTagsProvider => throw new NotImplementedException();
+        IGitMetadataTagsProvider IDatadogTracer.GitMetadataTagsProvider => new NullGitMetadataProvider();
 
-        PerTraceSettings IDatadogTracer.PerTraceSettings => throw new NotImplementedException();
+        PerTraceSettings IDatadogTracer.PerTraceSettings => null;
 
         void IDatadogTracer.Write(ArraySegment<Span> span)
         {
-            throw new NotImplementedException();
+           
         }
     }
 }