Remove unwraps in bdk_cli and more detailed message for ChecksumMismatch

[RCasatta]

Description

This removes some unwraps in favor of ? during handling of the commands.

During development I frequently hit ChecksumMismatch while changing the descriptor and keeping the same wallet name, I imagined users may be confused so I detailed the message.

Notes to the reviewers

On top of #22

Error handling is a little nicer for end-user but it comes at the expense of losing stacktrace information in case of errors, so it may be controversial. However, we are now writing blog post and expanding user base so I think it is better.

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 updated CHANGELOG.md

[thunderbiscuit]

Great idea! The ChecksumMismatch error message has been bugging me for some time now, and I think a more user-friendly explanation as to what is going on is a really good thing.

[notmandatory]

The reason we didn't add any default features is because the wasm playground app doesn't need repl and can't use electrum .. but maybe this is OK if we just build bitcoindevkit.org/playground with default-features = false and features=["esplora"]. @afilini does that sound ok?

[afilini]

Yes, exactly. As long as there's a way to disable them it should be fine

[notmandatory]

At some point I'd like to try adding anyhow to this project to add context to and help display errors, but I think we'd also need to add thiserror macro for bdk errors. For now I think the solution in the PR is a good step in the right direction.

[afilini]

This one probably needs rebasing after the force-push on #22

[RCasatta]

rebased