Update workflows

This PR includes changes from:
- #332: Use -C rathen than -Z for instrument-coverage
- #320: Replace unmaintained actions-rs/toolchain with dtolnay/rust-toolchain@master

It also updates actions/cache to v4.

.github/workflows/format.yml

@@ -10,10 +10,9 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Toolchain setup
-        uses: actions-rs/toolchain@v1
+        uses: dtolnay/rust-toolchain@master
         with:
           toolchain: nightly
-          override: true
           components: rustfmt
 
       - uses: actions/checkout@v4

.github/workflows/test.yaml

@@ -23,33 +23,32 @@ jobs:
     steps:
       - uses: actions/checkout@v4
       - name: Cache cargo registry
-        uses: actions/cache@v1
+        uses: actions/cache@v4
         with:
           path: ~/.cargo/registry
           key: ${{ runner.os }}-cargo-registry-${{ hashFiles('**/Cargo.lock') }}
       - name: Cache cargo index
-        uses: actions/cache@v1
+        uses: actions/cache@v4
         with:
           path: ~/.cargo/git
           key: ${{ runner.os }}-cargo-index-${{ hashFiles('**/Cargo.lock') }}
       - name: Cache cargo binaries
-        uses: actions/cache@v1
+        uses: actions/cache@v4
         with:
           path: ~/.cargo/bin
           key: ${{ runner.os }}-cargo-bin-${{ hashFiles('**/Cargo.lock') }}
       - name: Toolchain setup
-        uses: actions-rs/toolchain@v1
+        uses: dtolnay/rust-toolchain@master
         with:
           toolchain: nightly
-          override: true
           components: llvm-tools-preview
       - name: Install grcov
         if: matrix.rust-version == 'nightly' && matrix.cargo-args == '--all-features'
         run: if [[ ! -e ~/.cargo/bin/grcov ]]; then cargo install grcov; fi
       - name: Run tests
         run: cargo test --all-features --no-fail-fast
         env:
-          RUSTFLAGS: '-Zinstrument-coverage'
+          RUSTFLAGS: '-Cinstrument-coverage'
       - name: Run grcov
         if: matrix.rust-version == 'nightly' && matrix.cargo-args == '--all-features'
         # Important! Keep in grcov flags in sync with Makefile.internal.toml.