v2.0.2

The v2/blockstore.ReadWrite now offers Discard to allow closing the blockstore without performing the extra work done as part of Finalize. Apart from use in testing, this is particularly useful when writing a CARv2 file is cancelled.

Fixes an issue where v2/blockstore.ReadOnly blockstore would panic if used after it is closed. It now returns a dedicated error to signal that the blockstore is closed and no longer usable.

Fixes an issue where AllKeysChan retained lock when an error occurs early on during the traversal.

See #206

Full Changelog: v2.0.1...v2.0.2