Merge bitcoindevkit/bdk-cli#90: Disable regex tests when repl feature not enabled

953c097871d34d2606d55294313b1addc579dfa4 Disable regex tests when repl feature not enabled (Steve Myers)

Pull request description:

  ### Description

  I noticed that when I disable default features and don't enable the `repl` feature that the regex tests fail because they need the regex dependency that the `repl` feature brings in. This PR is to simply disable the regex related test code if the `repl` feature isn't enabled.

  ### Notes to the reviewers

  ### Checklists

  #### All Submissions:

  * [x] I've signed all my commits
  * [x] I followed the [contribution guidelines](https://github.com/bitcoindevkit/bdk-cli/blob/master/CONTRIBUTING.md)
  * [x] I ran `cargo fmt` and `cargo clippy` before committing

  #### New Features:

  * [ ] I've added tests for the new feature
  * [ ] I've added docs for the new feature
  * [ ] I've updated `CHANGELOG.md`

  #### Bugfixes:

  * [ ] This pull request breaks the existing API
  * [ ] 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:
  rajarshimaitra:
    ACK 953c097871d34d2606d55294313b1addc579dfa4

Tree-SHA512: b4aa8ecfc077bd06a578f5f8df054aff4dda496e7afd0c4f1d385aa1e5a5e2d452f8cf49fcc902abf2463a13ea0b99b38671262ea296c9a40243219731d0caa4