Convert StickerManagementRepository to kotlin.

Converts `StickerManagementRepository` to kotlin, so `getStickerPacks()` can return a `Flow` that emits updates after the database is changed.

This change simplifies the implementation of `StickerManagmentViewModelV2`, since `StickerManagementRepository.getStickerPacks()` will now automatically register and unregister the database observer.

app/src/main/java/org/thoughtcrime/securesms/database/StickerTable.kt

@@ -305,7 +305,7 @@ class StickerTable(
     notifyStickerListeners()
   }
 
-  fun updatePackOrder(packsInOrder: MutableList<StickerPackRecord>) {
+  fun updatePackOrder(packsInOrder: List<StickerPackRecord>) {
     writableDatabase.withinTransaction { db ->
       for ((i, pack) in packsInOrder.withIndex()) {
         db.update(TABLE_NAME)
@@ -470,6 +470,12 @@ class StickerTable(
       )
     }
 
+    fun asSequence(): Sequence<StickerPackRecord> = sequence {
+      while (getNext() != null) {
+        yield(getCurrent())
+      }
+    }
+
     override fun close() {
       cursor.close()
     }