fix: down syncs not being reflected in client app

[DominicGBauer]

Description

1. Fix the issue where client IDs were not matching leading to down syncs not being shown on the client app.
2. Fix updateObjectsFromBuckets always returning true.

Work Done

• There was an erroneously included ' at the end of clientId when hitting the write-checkpoint endpoint which I have now removed.
• Moved to writeTransaction in updateLocalTarget function as there is a write occurring in the transaction.
• Moved to use new delete_pending_buckets operation.
• updateObjectsFromBuckets now returns the response from

val res = tx.get("select last_insert_rowid()") { cursor ->
    cursor.getLong(0)!!
}

as opposed to the execute

res = tx.execute(
     "INSERT INTO powersync_operations(op, data) VALUES(?, ?)",
      listOf("sync_local", "")
)

which always returned 1 row updated and therefore always resolved to true

Testing

Screen.Recording.2024-10-08.at.5.21.22.PM.mov