[ASM] Log endpoints collection failures as warnings, not errors

Reading EndpointDataSource.Endpoints executes third-party code that can
throw for reasons outside our control. In the Azure Functions isolated
worker, FunctionsEndpointDataSource builds its endpoints lazily and
rejects malformed route templates, so collecting endpoints at Kestrel
startup surfaces a RoutePatternException.

Endpoints collection is best-effort and the failure does not affect the
application, so it should not be reported to telemetry as an error. The
other failure paths in the same method already use Log.Warning.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Author: dromanol

tracer/src/Datadog.Trace/ClrProfiler/AutoInstrumentation/AspNetCore/EndpointsCollection/KestrelServerImplStartAsyncIntegration.cs

@@ -57,7 +57,12 @@ internal static CallTargetState OnMethodBegin<TTarget, TApplication>(TTarget ins
         }
         catch (Exception ex)
         {
-            Log.Error(ex, "API Security: Failed to collect endpoints.");
+            // Reading EndpointDataSource.Endpoints runs third-party code that can throw for reasons
+            // outside our control (e.g. the Azure Functions worker builds its endpoints lazily and
+            // rejects a malformed route template). Endpoints collection is best-effort, so a failure
+            // here degrades the feature without affecting the application: warn rather than report
+            // an error to telemetry.
+            Log.Warning(ex, "API Security: Failed to collect endpoints.");
         }
 
         return CallTargetState.GetDefault();