New benchmark: Gesture semantics (#35232)

* Add semanticsEnabled to widgetBenchmark
* Add button_matrix_app and gesture benchmark
diff --git a/dev/benchmarks/microbenchmarks/README.md b/dev/benchmarks/microbenchmarks/README.md
index 7174a5d..eda8bae 100644
--- a/dev/benchmarks/microbenchmarks/README.md
+++ b/dev/benchmarks/microbenchmarks/README.md
@@ -6,6 +6,7 @@
 
 ```
 flutter run --release lib/gestures/velocity_tracker_data.dart
+flutter run --release lib/gestures/gesture_detector_bench.dart
 flutter run --release lib/stocks/animation_bench.dart
 flutter run --release lib/stocks/build_bench.dart
 flutter run --release lib/stocks/layout_bench.dart