Closes #4983: Fennec migration: Keep installed add-ons

app/src/main/java/org/mozilla/fenix/components/Components.kt

@@ -58,9 +58,6 @@ class Components(private val context: Context) {
         )
     }
 
-    /**
-     * Add-on
-     */
     val addonCollectionProvider by lazy {
         AddonCollectionProvider(context, core.client, maxCacheAgeInMinutes = DAY_IN_MINUTES)
     }

app/src/migration/java/org/mozilla/fenix/MigratingFenixApplication.kt

@@ -22,7 +22,11 @@ class MigratingFenixApplication : FenixApplication() {
                 this.components.core.passwordsEncryptionKey
             )
             .migrateFxa(this.components.backgroundServices.accountManager)
-            .migrateAddons(this.components.core.engine)
+            .migrateAddons(
+                this.components.core.engine,
+                this.components.addonCollectionProvider,
+                this.components.addonUpdater
+            )
             .migrateTelemetryIdentifiers()
             .build()
     }