Introduce image loading performance test. (#34823)

* Introduce image loading performance test.

This example reports how long it takes to load images over the network(locally spawned server).

examples/image_list/android/settings.gradle

diff --git a/examples/image_list/android/settings.gradle b/examples/image_list/android/settings.gradle
new file mode 100644
index 0000000..5a2f14f
--- /dev/null
+++ b/examples/image_list/android/settings.gradle
@@ -0,0 +1,15 @@
+include ':app'
+
+def flutterProjectRoot = rootProject.projectDir.parentFile.toPath()
+
+def plugins = new Properties()
+def pluginsFile = new File(flutterProjectRoot.toFile(), '.flutter-plugins')
+if (pluginsFile.exists()) {
+    pluginsFile.withReader('UTF-8') { reader -> plugins.load(reader) }
+}
+
+plugins.each { name, path ->
+    def pluginDirectory = flutterProjectRoot.resolve(path).resolve('android').toFile()
+    include ":$name"
+    project(":$name").projectDir = pluginDirectory
+}