Airbyte loaders: Fix last_state getter (#9314)
This PR fixes the Airbyte loaders when doing incremental syncs. The
notebooks are calling out to access `loader.last_state` to get the
current state of incremental syncs, but this didn't work due to a
refactoring of how the loaders are structured internally in the original
PR.
This PR fixes the issue by adding a `last_state` property that forwards
the state correctly from the CDK adapter.
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Co-authored-by: Bagatur <baskaryan@gmail.com>
