Merge bitcoindevkit/bdk#765: Fix how descriptor checksums are calculated

648282e60283f579ba1644fe506ae1370786da96 Update docs and tests based on review comments (Steve Myers)
60057a7bf78f01bfb1149251f384de6432f94d59 Deprecate backward compatible get_checksum_bytes, get_checksum functions (Steve Myers)
e2a4a5884b444a6ef3f137ef2cc21a816c386acf Ensure backward compatibility of the  "checksum inception" bug (志宇)
fd34956c2980295e1f0cc32340fb2b99a6b245ea `get_checksum_bytes` now checks input data for checksum (志宇)

Pull request description:

  ### Description

  Previously, the methods `get_checksum_bytes` and `get_checksum` do not check input data to see whether the input data already has a checksum.

  This PR does the following:

  * Introduce a `exclude_hash: bool` flag for `get_checksum_bytes`, that excludes the checksum portion of the original data when calculating the checksum. In addition to this, if the calculated checksum does not match the original checksum, an error is returned for extra safety.
  * Ensure `Wallet` is still backwards compatible with databases created with the "checksum inception" bug.

  ### Notes to the reviewers

  Thank you.

  ### Changelog notice

  Fix the "checksum inception" bug, where we may accidentally calculate the checksum of a descriptor that already has a checksum.

  ### 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:

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

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Tree-SHA512: 7ea2721dcd56459b6996e56a3ddfc3559a0c64869a08f5312a8f0f4fcb5dbef7ac7461a4ab017acde4a62fed02d8a620c402dd384323aba85736610514fcb7e1