Merge bitcoindevkit/bdk#814: Improve display error formatting

Merge bitcoindevkit/bdk#814: Improve display error formatting

9019793bd4090d704b17876c57bf255a75507ed2 Improve display error formatting (Yuki Kishimoto)

Pull request description:

  ### Description

  Closes #555

  ### Checklists

  #### All Submissions:

  * [X] I've signed all my commits
  * [X] I followed the [contribution guidelines](https://github.com/bitcoindevkit/bdk/blob/master/CONTRIBUTING.md)
  * [X] I ran `cargo fmt` and `cargo clippy` before committing

  #### Bugfixes:

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

ACKs for top commit:
  notmandatory:
    ACK 9019793bd4090d704b17876c57bf255a75507ed2

Tree-SHA512: 44f0c7e0374e255bf99cbbfb01f2af76746e52afe67ace1595d2830bd60be99f3c8726e6ad9744878978257796a79b3933e7ef21c30a5e4b99a16aaf9ac7ff64