Bug 40016: Allow inheriting from AddonCollectionProvider

This will allow implementing our own AddonsProvider in fenix.

components/feature/addons/src/main/java/mozilla/components/feature/addons/amo/AddonCollectionProvider.kt

@@ -58,7 +58,7 @@ internal const val PAGE_SIZE = 50
  * cache is being used by default
  */
 @Suppress("LongParameterList")
-class AddonCollectionProvider(
+open class AddonCollectionProvider(
     private val context: Context,
     private val client: Client,
     private val serverURL: String = DEFAULT_SERVER_URL,
@@ -156,7 +156,7 @@ class AddonCollectionProvider(
      * a connectivity problem or a timeout.
      */
     @Throws(IOException::class)
-    suspend fun getAddonIconBitmap(addon: Addon): Bitmap? {
+    open suspend fun getAddonIconBitmap(addon: Addon): Bitmap? {
         var bitmap: Bitmap? = null
         if (addon.iconUrl != "") {
             client.fetch(
@@ -174,7 +174,7 @@ class AddonCollectionProvider(
     }
 
     @VisibleForTesting
-    internal fun writeToDiskCache(collectionResponse: String) {
+    protected fun writeToDiskCache(collectionResponse: String) {
         synchronized(diskCacheLock) {
             getCacheFile(context).writeString { collectionResponse }
         }