Merge bitcoindevkit/bdk#1989: chore(bdk-electrum): use new `batch_transaction_get_mer...

Merge bitcoindevkit/bdk#1989: chore(bdk-electrum): use new `batch_transaction_get_merkle` API

b663940ac3c81f57589f13bcc49dc1f8b483dc74 chore(bdk-electrum): use new `batch_transaction_get_merkle` API (Leonardo Lima)

Pull request description:

  fixes #1987
  depends on https://github.com/bitcoindevkit/rust-electrum-client/pull/170

  ### Description

  - update `batch_fetch_anchors` to use `batch_transaction_get_merkle` method instead of manually creating the batch call.

  ### Changelog notice

  ```md
  ### Changes
  - Use new `batch_transaction_get_merkle` method instead of batch raw calls
  ```

  ### 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 +nightly fmt` and `cargo clippy` before committing

ACKs for top commit:
  ValuedMammal:
    ACK b663940ac3c81f57589f13bcc49dc1f8b483dc74
  LagginTimes:
    ACK b663940ac3c81f57589f13bcc49dc1f8b483dc74

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