Rework sqlite: Instead of only supported one schema (defined in
`bdk_sqlite`), we have a schema per changeset type for more flexiblity.
* rm `bdk_sqlite` crate (as we don't need `bdk_sqlite::Store` anymore).
* add `sqlite` feature on `bdk_chain` which adds methods on each
changeset type for initializing tables, loading the changeset and
writing.
Rework changesets: Some callers may want to use `KeychainTxOutIndex`
where `K` may change per descriptor on every run. So we only want to
persist the last revealed indices by `DescriptorId` (which uniquely-ish
identifies the descriptor).
* rm `keychain_added` field from `keychain_txout`'s changeset.
* Add `keychain_added` to `CombinedChangeSet` (which is renamed to
`WalletChangeSet`).
Rework persistence: add back some safety and convenience when persisting
our types. Working with changeset directly (as we were doing before) can
be cumbersome.
* Intoduce `struct Persisted<T>` which wraps a type `T` which stores
staged changes to it. This adds safety when creating and or loading
`T` from db.
* `struct Persisted<T>` methods, `create`, `load` and `persist`, are
avaliable if `trait PersistWith<Db>` is implemented for `T`. `Db`
represents the database connection and `PersistWith` should be
implemented per database-type.
* For async, we have `trait PersistedAsyncWith<Db>`.
* `Wallet` has impls of `PersistedWith<rusqlite::Connection>`,
`PersistedWith<rusqlite::Transaction>` and
`PersistedWith<bdk_file_store::Store>` by default.
Rework wallet-construction: Before, we had multiple methods for loading
and creating with different input-counts so it would be unwieldly to add
more parameters in the future. This also makes it difficult to impl
`PersistWith` (which has a single method for `load` that takes in
`PersistWith::LoadParams` and a single method for `create` that takes in
`PersistWith::CreateParams`).
* Introduce a builder pattern when constructing a `Wallet`. For loading
from persistence or `ChangeSet`, we have `LoadParams`. For creating a
new wallet, we have `CreateParams`.
All `Wallet` constructors are modified to require a change
descriptor, where previously it was optional. Additionally
we enforce uniqueness of the change descriptor to avoid
ambiguity when deriving scripts and ensure the wallet will
always have two distinct keystores.
Notable changes
* Add error DescriptorError::ExternalAndInternalAreTheSame
* Remove error CreateTxError::ChangePolicyDescriptor
* No longer rely on `map_keychain`
