Modify Addon support

Bug 40011: Hide option for disallowing addons in private mode

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,
@@ -173,7 +173,7 @@ 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(
@@ -191,7 +191,7 @@ class AddonCollectionProvider(
     }
 
     @VisibleForTesting
-    internal fun writeToDiskCache(collectionResponse: String, language: String?) {
+    protected fun writeToDiskCache(collectionResponse: String, language: String?) {
         synchronized(diskCacheLock) {
             getCacheFile(context, language, useFallbackFile = false).writeString { collectionResponse }
         }

components/feature/addons/src/main/res/layout/mozac_feature_addons_fragment_dialog_addon_installed.xml

@@ -63,6 +63,7 @@
         />
 
     <androidx.appcompat.widget.AppCompatCheckBox
+        android:visibility="gone"
         android:id="@+id/allow_in_private_browsing"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"

samples/browser/src/main/res/layout/activity_installed_add_on_details.xml

@@ -70,6 +70,7 @@
                 app:drawableStartCompat="@drawable/mozac_ic_permissions" />
 
         <SwitchCompat
+            android:visibility="gone"
             android:id="@+id/allow_in_private_browsing_switch"
             android:layout_width="match_parent"
             android:layout_height="wrap_content"