Merge bitcoindevkit/bdk#1623: fix!(wallet): `ChangeSet` should not be non-exhaustive

d7dfe38ff6c0f1b984e15defc83c79e52a44afa9 fix!(wallet): `ChangeSet` should not be non-exhaustive (志宇)

Pull request description:

  Closes #1591

  ### Description

  As stated in #1591, it is handy to know when new values are added to `ChangeSet`.

  ### Notes to the reviewers

  ~

  ### Changelog notice

  * Remove `#[non_exhaustive]` attribute from `wallet::ChangeSet`.

  ### 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

ACKs for top commit:
  oleonardolima:
    utACK d7dfe38ff6c0f1b984e15defc83c79e52a44afa9
  ValuedMammal:
    ACK d7dfe38ff6c0f1b984e15defc83c79e52a44afa9

Tree-SHA512: 2856d9af625ee788c5ddec0a51dace26a1cb1b57b327ffb8439fe8a45888cdf2ecaeac8d2c777620f83b66d211bac4d17fea3d1143800127316ba475b5064b23