Add new crate bdk-persist

[rustaceanrob]

Description

#1387 introduced anyhow as a dependency to remove generics from Wallet. Introducing a new crate for persistence types removes the dependency on anyhow for bdk_chain. Resolves #1409, as well as removing the old documentation for "tracker".

Notes to the reviewers

Open for any comments.

Changelog notice

• Introduce bdk-persist crate

Checklists

All Submissions:

• I've signed all my commits
• I followed the contribution guidelines
• I ran cargo fmt and cargo clippy before committing

New Features:

• I've added tests for the new feature
• I've added docs for the new feature

Bugfixes:

• This pull request breaks the existing API
• I've added tests to reproduce the issue which are now passing
• I'm linking the issue being fixed by this PR

[ValuedMammal]

Additional note that the wallet README has links to PersistBackend that should be updated to point to the new bdk_persist crate. So far, that's the only other thing that stood out to me.

[rustaceanrob]

Thanks for those suggestions, updated

[ValuedMammal]

LGTM. I built and ran the example crates to check that persistence still works, also built the docs locally and found no issues (assuming the new crate will be published to docs.rs).

[rustaceanrob]

Thanks for those checks, appreciate it. I also clicked around the docs locally and it linked properly. Think I caught them all with a grep. Might do one final pass for any bdk-chain references to one of the bdk-persist traits but hopefully its all good.

[storopoli]

Just a minor check: are we adding the new bdk_persist to CI? Or is it already covered by default?

[evanlinjin]

ACK 81de8f6

[evanlinjin]

Nit: *Types used for persisting bdk_chain data.