Centralize the logic for adding golden assets for tests

This moves the logic for all the libraries that follow a standard golden
path. There will be a follow up the moves the rest.

Test: ./gradlew ink:ink-authoring:assembleAndroidTest -> assets still
      there
Change-Id: I2ac781b5d6cf029a8c680f865e0a0ac5fc52ba26
diff --git a/glance/glance-wear-tiles/build.gradle b/glance/glance-wear-tiles/build.gradle
index da875d3..a21f20d 100644
--- a/glance/glance-wear-tiles/build.gradle
+++ b/glance/glance-wear-tiles/build.gradle
@@ -84,12 +84,7 @@
         // protobuf generates unannotated methods
         disable "UnknownNullness"
     }
-
-    sourceSets {
-        androidTest.assets.srcDirs += project.rootDir.absolutePath + "/../../golden/glance/glance-wear-tiles"
-    }
     namespace = "androidx.glance.wear.tiles"
-
 }
 
 androidx {
@@ -101,4 +96,5 @@
             "Compose-style API."
     legacyDisableKotlinStrictApiMode = true
     metalavaK2UastEnabled = false
+    addGoldenImageAssets()
 }