Merge bitcoindevkit/bdk#2054: fix(ci,test): update `chained_mempool_txs` to use 6...

Merge bitcoindevkit/bdk#2054: fix(ci,test): update `chained_mempool_txs` to use 6 secs timeout

353d18bd69b9bfe0d70cf8e0658a98dabf44bb1f fix(ci,test): update `chained_mempool_txs` to use 6 secs timeout (Leonardo Lima)

Pull request description:

  fixes #2045

  ### Description

  It's an initial attempt to solve the timeout failures we have been facing on CI when running electrum tests. It it's not solved at all, at least it now adds the total time elapsed so we can know how long it's taking in CI.

  The PR updates the `chained_mempool_txs` test to use 6 seconds as timeout, instead of 5, it was the only spot using 5 instead of 6. Also updates the error message to show the total time elapsed, can help debug the CI if the timeout error persists.

  ### Notes to the reviewers

  ### Changelog notice

  ```
  ### Changed
  - Update the `chained_mempool_txs` to use 6 seconds as timeout.
  - Update the error message to show the time elapsed.
  ```

  ### Checklists

  #### All Submissions:

  * [x] I followed the [contribution guidelines](https://github.com/bitcoindevkit/bdk/blob/master/CONTRIBUTING.md)

ACKs for top commit:
  evanlinjin:
    ACK 353d18bd69b9bfe0d70cf8e0658a98dabf44bb1f

Tree-SHA512: 62edc397ca74dd8b3a90eb300ea8d52772b3089698d8dad481bf2f9e4ef394ab2a826abdfa7f5d177e675a03bb83ac56445273dbc1d35885ff78651ec9bfc5aa