…` serialization.

…canning.

Also adds a skeleton `zcash_client_sqlite` implementation of
`shardtree::ShardStore` and a skeleton migration for related
database changes.

…alletWrite::put_block`

Also, add assertions to prevent attempting the creation of zero-conf
shielded spends.

…aled issues.

… it reusable for Orchard.

…the `wallet::sapling` module.

…lock.

We move thes fields out into a separate BlockMetadata struct to ensure
that future additions to block metadata are structurally separated from
future additions to block data.

Co-authored-by: str4d <[email protected]>

…ning.

Local chain validation will be performed internal to
`scan_cached_blocks`, and as handling of chain reorgs will need to
change to support out-of-order scanning, the `validate_chain` method
will be superfluous. It is removed in advance of other changes in order
to avoid updating it to reflect the forthcoming changes.

In preparation for out-of-order range-based scanning, it is necessary
to ensure that the size of the Sapling note commitment tree is carried
along through the scan process and that stored blocks are always
persisted with the updated note commitment tree size.

…scanning`