Added a benchmark for ImageCache (#33814)

* Add an image cache benchmark for a monochrome image

dev/devicelab/manifest.yaml

diff --git a/dev/devicelab/manifest.yaml b/dev/devicelab/manifest.yaml
index 9392670..02b57ce 100644
--- a/dev/devicelab/manifest.yaml
+++ b/dev/devicelab/manifest.yaml
@@ -527,6 +527,13 @@
     stage: devicelab
     required_agent_capabilities: ["linux/android"]
 
+  flutter_gallery__image_cache_memory:
+    description: >
+      Measures memory usage for a list of large red squares in smaller containers.
+    stage: devicelab
+    required_agent_capabilities: ["linux/android"]
+    flaky: true
+
   analyzer_benchmark:
     description: >
       Measures the speed of Dart analyzer.