Merge bitcoindevkit/bdk-ffi#175: Set project MSRV to 1.57.0

6d53cbeb2502602d1bab0fd11f63d203f61b507a Fix fmt error (Steve Myers)
1a12f37a2f1c5f99e3b590b3ba070859120a9f8e Set MSRV to 1.57.0 (Steve Myers)

Pull request description:

  ### Description

  The `master` branch is currently not passing the new github checks.

  A required dependency of `bdk-ffi-bindgen` is `uniffi_bindgen` and it depends on `os_str_bytes` v6.2.0 which has a MSRV of 1.57.0. I therefore had to make the MSRV of `bdk-ffi` also 1.57.0 and update the github actions. This PR also fixes a small `cargo fmt` warning.

  ### Notes to the reviewers

  ```shell
  % cargo +1.56.1 build
  error: package `os_str_bytes v6.2.0` cannot be built because it requires rustc 1.57.0 or newer, while the currently active rustc version is 1.56.1
  ```

  ```shell
  % cargo tree -i os_str_bytes
  os_str_bytes v6.2.0
  └── clap_lex v0.2.4
      └── clap v3.1.18
          └── uniffi_bindgen v0.19.3
              └── bdk-ffi-bindgen v0.2.0 (/Users/steve/git/notmandatory/bdk-ffi/bdk-ffi-bindgen)
  ```

  ### 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

Top commit has no ACKs.

Tree-SHA512: 87ad4a02d91184b421871354b1f5c31d906bf7460fe992db15666da32a65f13d8fbaf4ae53928f410a7206b195c8dff76af07210c144a4d02854ceb6af265f7e

.github/workflows/cont_integration.yml

@@ -12,7 +12,7 @@ jobs:
         rust:
           - version: 1.60.0 # STABLE
             clippy: true
-          - version: 1.56.1 # MSRV
+          - version: 1.57.0 # MSRV
     steps:
       - name: checkout
         uses: actions/checkout@v2

bdk-ffi-bindgen/src/main.rs

@@ -1,8 +1,8 @@
+use camino::Utf8Path;
 use std::fmt;
 use std::path::{Path, PathBuf};
 use std::str::FromStr;
 use structopt::StructOpt;
-use camino::Utf8Path;
 
 #[derive(Debug, PartialEq)]
 pub enum Language {