[Demo] Add BIP322 implementation

[aagbotemi]

Description

This PR implements the BIP322 standard for generic signed message in Bitcoin

Features

• Core message signing and verification
• Support for Legacy, Simple and Full
• Test suites to cover edge cases
• Comments to explain functionality

Notes to the reviewers

This PR is intended as demonstration of BIP322 and it is open for feedback

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

[notmandatory]

fixes bitcoindevkit/bdk_wallet#150

[notmandatory]

@aagbotemi please rebase this PR to fix the CI issues.

Also this is a pretty big PR that will need careful review due to the use of private keys. Please be patient as it will take some time to get proper reviews done. Thanks!

[aagbotemi]

Hi @notmandatory. I have rebased this PR.

[luisschwab]

Hey @aagbotemi, this PR needs to be closed and moved to the new bdk_wallet repo. Here's how:

1. From your Github account, fork https://github.com/bitcoindevkit/bdk_wallet
2. From your local system bdk repo folder, push your PR changes to your bdk_wallet fork on Github:

   git checkout <PR branch path>
   git push [email protected]:<username>/bdk_wallet.git
   

3. Clone to your forked bdk_wallet repo to your local system and switch to your PR branch:

   git clone [email protected]:<username>/bdk_wallet.git
   cd bdk_wallet
   git fetch origin <PR branch path>
   git checkout -b <PR branch path> FETCH_HEAD
   git rebase master
   

4. Resolve rebase conflicts (if any)
5. Force push your PR branch: git push origin -f
6. Create new PR in bitcoindevkit/bdk_wallet repo from your fork branch
7. Copy/paste title and description from your original bdk PR and add a link back to it in your new PR.
8. Close original PR with comment that includes link to new PR.