Merge bitcoindevkit/bdk#1246: Fix: apply loaded changeset to indexed_graph when loadi...

f4863c6314904ddd5da586fed0abb8f04ccee396 fix(wallet): apply loaded changeset to indexed_graph (thunderbiscuit)

Pull request description:

  ### Description
  This PR applies the tx_graph from the changeset when loading a wallet from persistence. This ensures among other things that the revealed keychain indices get picked up by the new wallet. A test for this has been added/modified from an old test.

  ### Notes to the reviewers

  ### Changelog notice
  Fix: loading a wallet from persistence now restores keychain indices.

  ### 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
  * [x] I've added tests to reproduce the issue which are now passing
  * [ ] I'm linking the issue being fixed by this PR

ACKs for top commit:
  evanlinjin:
    ACK f4863c6314904ddd5da586fed0abb8f04ccee396

Tree-SHA512: c8502077ba25e6fb953829b020b396774aa0569f7272e7818f30ddabed9d1d8ce791729bebc92b9ec1059028399495cb79ea147cf900f25aace94045dd7290a6