Merge #1077: fix: msrv issues

b0b91b7 fix: msrv issues and update coverage toolchain (Vladimir Fomene)

Pull request description:

  Fix breaking MSRV for 1.57.0

  #### 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:
  danielabrozzoni:
    ACK b0b91b7

Tree-SHA512: d872f427da065c66346f0fd3ae19d4d62c535cf4444d236c0d1f6e9a5e169b7fd7773f643693daa23eeccbe6a3ddad6767f91520c7547360c07febc227a88f06

.github/workflows/code_coverage.yml

@@ -19,7 +19,7 @@ jobs:
       - name: Install Rust toolchain
         uses: actions-rs/toolchain@v1
         with:
-            toolchain: "1.65.0"
+            toolchain: "1.67.0"
             override: true
             profile: minimal
             components: llvm-tools-preview

.github/workflows/cont_integration.yml

@@ -29,7 +29,12 @@ jobs:
         uses: Swatinem/[email protected]
       - name: Pin dependencies for MSRV
         if: matrix.rust.version == '1.57.0'
-        run: cargo update -p log --precise "0.4.18" && cargo update -p tempfile --precise "3.6.0" && cargo update -p rustls:0.21.6 --precise "0.21.1"
+        run: |
+          cargo update -p log --precise "0.4.18"
+          cargo update -p tempfile --precise "3.6.0"
+          cargo update -p rustls:0.21.6 --precise "0.21.1"
+          cargo update -p tokio:1.31.0 --precise "1.29.1"
+          cargo update -p flate2:1.0.27 --precise "1.0.26"
       - name: Build
         run: cargo build ${{ matrix.features }}
       - name: Test