Merge bitcoindevkit/bdk#1282: Bump version to 1.0.0-alpha.4

Merge bitcoindevkit/bdk#1282: Bump version to 1.0.0-alpha.4

d33acc14661326972b3ab3cf2b7cee4ca078f4da Bump version to 1.0.0-alpha.4 (Steve Myers)

Pull request description:

  ### Description

  Bump version to 1.0.0-alpha.4, also:

  bdk_chain to 0.8.0
  bdk_bitcoind_rpc to 0.3.0
  bdk_electrum to 0.6.0
  bdk_esplora to 0.6.0
  bdk_file_store to 0.4.0

  Fixes #1281.

  ### Notes to the reviewers

  Since the version of bdk_chain changed all crates that depend on it also need to have their versions bumped.

  ### 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:
  evanlinjin:
    ACK d33acc14661326972b3ab3cf2b7cee4ca078f4da

Tree-SHA512: ffb5c05b45e9d646ef796bd894353e4b58c3aae3dcf0921dfb9fcae45020ed4fc82274a7497494d6259bfffff9c2f97c530d2cbe6ace578babd04852af461f3a