Feature: Checkpoint when closing db or Recover when attaching to external Kuzu db

[semihsalihoglu-uw]

API

Python

Description

We currently allow attaching to a remote Kuzu db if its wal file is empty. However with the new MVCC mechanism, wal files will generally be non-empty. This means we cannot attach to (most) Kuzu dbs. There are two things to do here:

1. Remedy: A good remedy is to checkpoint before closing dbs and remove the wal file contents. We can assume that users would close external dbs before attaching to them. So, this should ensure that the external dbs we attach to have empty wal files.
2. Solution: Attach db functionality does not assume that the wal file is empty. This is apparently also doable.

If the remedy is easy to do, I suggest we just do that and keep this issue open until we have enough time to implement the actual solution. If they're about the same amount of work, we can go for the solution and not implement the remedy.