feat: Add new enableCodeScanner prop to build.gradle to make sure CodeScanner always works (#2355)

* feat: Always download model instead of relying on Google Play Services

* feat: Use `VisionCamera_enableCodeScanner` flag instead of unsafely replacing

* Update CODE_SCANNING.mdx

package/android/build.gradle

@@ -71,6 +71,8 @@ def nodeModules = findNodeModules(projectDir)
 def hasWorklets = !safeExtGet("VisionCamera_disableFrameProcessors", false) && findProject(":react-native-worklets-core") != null
 logger.warn("[VisionCamera] react-native-worklets-core ${hasWorklets ? "found" : "not found"}, Frame Processors ${hasWorklets ? "enabled" : "disabled"}!")
 
+def enableCodeScanner = safeExtGet("VisionCamera_enableCodeScanner", false)
+
 repositories {
   google()
   mavenCentral()
@@ -162,7 +164,15 @@ dependencies {
   //noinspection GradleDynamicVersion
   implementation "com.facebook.react:react-android:+"
   implementation "org.jetbrains.kotlinx:kotlinx-coroutines-android:1.5.2"
-  implementation "com.google.android.gms:play-services-mlkit-barcode-scanning:18.3.0"
+
+  if (enableCodeScanner) {
+    // User enabled code-scanner, so we bundle the 2.4 MB model in the app.
+    implementation 'com.google.mlkit:barcode-scanning:17.2.0'
+  } else {
+    // Fall-back to just including the code for the CodeScanner to avoid the 2.4 MB bundle in the app.
+    // On devices with Google Play Services, this can also download the CodeScanner model on-demand.
+    implementation "com.google.android.gms:play-services-mlkit-barcode-scanning:18.3.0"
+  }
 
   if (hasWorklets) {
     // Frame Processor integration (optional)