Use TotalMilliseconds instead of TimeSpan in delay telemetry (#76309)

Just noticed that recent telemetry change #76045 uses Timestamp to
report delay, e.g. `00:00:00.0006369`. Processing timestamp is
expensive. I'm updating telemetry to use `double TotalMillseconds`, e.g.
`68.9512` (sic, this example is pasted from a different measurement)

src/EditorFeatures/Core.Wpf/InlineRename/UI/SmartRename/SmartRenameViewModel_Telemetry.cs

@@ -54,7 +54,7 @@ private void PostTelemetry(bool isCommit)
                     m["smartRenameSessionInProgress"] = _smartRenameSession.IsInProgress;
                     m["smartRenameCorrelationId"] = _smartRenameSession.CorrelationId;
                     m["smartRenameSemanticContextUsed"] = _semanticContextUsed;
-                    m["smartRenameSemanticContextDelay"] = _semanticContextDelay;
+                    m["smartRenameSemanticContextDelay"] = _semanticContextDelay.TotalMilliseconds;
                     m["smartRenameSemanticContextError"] = _semanticContextError;
                 }));
             }
@@ -69,7 +69,7 @@ private void PostTelemetry(bool isCommit)
                     m["smartRenameSessionInProgress"] = _smartRenameSession.IsInProgress;
                     m["smartRenameCorrelationId"] = _smartRenameSession.CorrelationId;
                     m["smartRenameSemanticContextUsed"] = _semanticContextUsed;
-                    m["smartRenameSemanticContextDelay"] = _semanticContextDelay;
+                    m["smartRenameSemanticContextDelay"] = _semanticContextDelay.TotalMilliseconds;
                     m["smartRenameSemanticContextError"] = _semanticContextError;
                 }));
             }