Merge bitcoindevkit/bdk#1805: feat(wallet): support Testnet4 in valid networks

c8e8a6a57fe17c683584774834a71a1bca5190d4 feat(wallet): support Testnet4 in valid networks (valued mammal)

Pull request description:

  Adds support for `Testnet4` in valid networks.

  fixes #1429

  ### Notes to the reviewers

  The `Testnet4` variant is included in `keys::any_network` and `keys::test_networks`. Tests are updated accordingly and a new assertion is added to `test_descriptor_from_str_with_keys_network` checking the result of `into_wallet_descriptor` when the specified network is `Network::Testnet4`.

  ### Changelog notice

  Added:
  - `Wallet` can now be constructed using `Network::Testnet4`

  ### 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:
  notmandatory:
    ACK c8e8a6a57fe17c683584774834a71a1bca5190d4

Tree-SHA512: e52642a799d1d781ad708d61ae9e78d18ecb7ad03df1e1feb6babe5067fa02859a2214b92b9d35b6922d40a606ed99163189c4cac8bbcc709edec970c1e136a4