Merge bitcoindevkit/bdk-cli#65: Auto deploy regtest nodes in background

Merge bitcoindevkit/bdk-cli#65: Auto deploy regtest nodes in background

930b0c48fef484e5b586346ca295358a3d30bb5e Update CHANGELOG (rajarshimaitra)
cf9f536db4c5ec31dcfd3054e1b01a8f6907f9ea Add CI build for new features (rajarshimaitra)
58a624b97f66f6d82b562f17661f66ff16dd95e7 Add auto backend deployment (rajarshimaitra)

Pull request description:

  <!-- You can erase any parts of this template not applicable to your Pull Request. -->

  ### Description

  Fixes https://github.com/bitcoindevkit/bdk-cli/issues/55. I decided to go for one feature flag for each backends as they made dependency management easier. Because different backend will have different dependency, and we don't wanna have redundant ones. Also it makes the commands a little shorter.

  ### Notes to the reviewers

  Right now its not that useful because the backend APIs are not exposed. So I can't really do much other than sync/send in the command line. (unlike testnet we cannot send coins to bdk from outside of local regtest node). So to make it useful in repl mode as described in the issue, we also have to expose the blockchain apis in bdk-cli command in some way (at least the basic stuffs, address, send, generate). Looking for suggestions on this.

  usage looks like this:
  ```
  cargo run --features regtest-rpc -- wallet --descriptor "wpkh(tpubEBr4i6yk5nf5DAaJpsi9N2pPYBeJ7fZ5Z9rmN4977iYLCGco1VyjB9tvvuvYtfZzjD5A8igzgw3HeWeeKFmanHYqksqZXYXGsw5zjnj7KM9/*)" sync
  {}
  ```

  Although I am having trouble connecting to the esplora end of electrs. Not sure whats the issue, will have to look more.

  ### 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
  * [x] I've updated `CHANGELOG.md`

ACKs for top commit:
  notmandatory:
    ACK 930b0c48fef484e5b586346ca295358a3d30bb5e

Tree-SHA512: a308398d30743c049a6c641f1cdcbf0643f11e56323b98a176c86ac237249beb2ac22b2802dd14fda7874a2079aaf25cacf60d082fd57109d6a41cff359b0145