project: check-in Cargo.lock file, use --locked

This matches updated guidance from the Rust project that libraries
_should_ check in their lockfile. Also updates CI to use `--locked`
where appropriate.

.github/workflows/rust.yml

@@ -41,26 +41,26 @@ jobs:
           toolchain: ${{ matrix.rust }}
 
       - name: cargo build (debug; default features)
-        run: cargo build
+        run: cargo build --locked
 
       - name: cargo test (debug; default features)
-        run: cargo test
+        run: cargo test --locked
         env:
           RUST_BACKTRACE: 1
 
       - name: cargo test (debug; all features)
-        run: cargo test --all-features
+        run: cargo test --locked --all-features
         env:
           RUST_BACKTRACE: 1
 
       - name: cargo build (debug; no default features)
-        run: cargo build --no-default-features
+        run: cargo build --locked --no-default-features
 
       - name: cargo test (debug; no default features; no run)
-        run: cargo test --no-default-features --no-run
+        run: cargo test --locked --no-default-features --no-run
 
       - name: cargo test (release; no run)
-        run: cargo test --release --no-run
+        run: cargo test --locked --release --no-run
 
       - name: run macOS integration test
         if: matrix.os == 'macos-latest'
@@ -83,7 +83,7 @@ jobs:
         with:
           toolchain: "1.60"
 
-      - run: cargo check --lib --all-features
+      - run: cargo check --locked --lib --all-features
 
   format:
     name: Format
@@ -112,4 +112,4 @@ jobs:
         uses: dtolnay/rust-toolchain@stable
         with:
           components: clippy
-      - run: cargo clippy --all-features -- --deny warnings
+      - run: cargo clippy --locked --all-features -- --deny warnings

.gitignore

@@ -1,4 +1,3 @@
-Cargo.lock
 target/
 *.gcda
 *.gcno