feat: add warning if crud transactions are not completed

[DominicGBauer]

Description

This implements the same change from the JS SDK powersync-ja/powersync-js#254 where a warning is added to notify users that the crud transaction has not yet been completed.

Work Done

• Added nextCrudItem function
• Updated uploadAllCrud function to use nextCrudItem with a check for uncompleted crud transaction
• Removed no longer used uploadCrudBatch
• To make things more testable I needed to create interfaces to mock, as mocking classes requires the classes to be open which we do not want (https://mokkery.dev/docs/Guides/Mocking#final-classes).
• In order to improve unit testing in Kotlin I have added the Mokkery library to handle mocking. The reason is that it appears to be one of two with mockative looking for maintainers.
• I have also started to move away from using powerSyncQueries, which is defined in the persistence model, as it makes testing impossible and is not very intuitive for developers working on the project. It also doesn't really provide much of an advantage besides typing the queries which can be achieved differently as shown in the replacement code. Example of moving from this:

val firstEntry = internalDb.queries.getCrudFirstEntry().awaitAsOneOrNull()

            val first = CrudEntry.fromRow(
                CrudRow(
                    id = firstEntry.id.toString(),
                    data = firstEntry.data_!!,
                    txId = firstEntry.tx_id?.toInt()
                )
            )

to this:

        val crudItem = db.getOptional("SELECT id, tx_id, data FROM ${InternalTable.CRUD} ORDER BY id ASC LIMIT 1") { cursor ->
            CrudEntry.fromRow(
                CrudRow(
                    id = cursor.getString(0)!!,
                    txId = cursor.getString(1)?.toInt(),
                    data = cursor.getString(2)!!
                )
            )
        }

Testing

Added some unit tests, although they will need to be improved in future as they currently check for log output which is not ideal.

Unsure on how to reproduce this in the demo, however, the image below shows that the error would show (this happened when changing nextCrudItem.clientId == checkedCrudItem?.clientId to nextCrudItem.clientId != checkedCrudItem?.clientId). I have run the app and uploads are working as expected.

Nevermind this was due to a logic error:

This is currently happening in the demo and may be related to a bug I am busy diagnosing

[mugikhan]

Great work on adding some tests. Looks good to me.