message: ci: switch to dtolnay/rust-toolchain
  The actions-rs/toolchain we were using appears dead:
  Here's dtolnay's take:
  In particular, it looks like a much more maintainable path here. For
  this one, if it ever goes unmaintained, I can maintain it myself without
  too much fuss.
  See also:
diff: @@ -64,11 +64,9 @@ jobs:
  uses: actions/checkout@v3
  - name: Install Rust
  - uses: actions-rs/toolchain@v1
  + uses: dtolnay/rust-toolchain@v1
  with:
  - override: true
  toolchain: ${{ matrix.rust }}
  - profile: minimal
  - name: Install and configure Cross
  if: matrix.target != ''
  @@ -163,11 +161,9 @@ jobs:
  - name: Checkout repository
  uses: actions/checkout@v3
  - name: Install Rust
  - uses: actions-rs/toolchain@v1
  + uses: dtolnay/rust-toolchain@v1
  with:
  - override: true
  toolchain: stable
  - profile: minimal
  components: rustfmt
  - name: Check formatting
  run: |
  