feat(coverage): Reduce coverage false-negatives using grcov

Previously, we would report some tag style macros such as
`#[repr(packed)]` as being uncovered.

We are now also including doctests in our coverage reports.

Finally, a new script `coverage_report.sh` makes coverage checking
easier.

.github/workflows/qc.yaml

@@ -194,19 +194,17 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
+      - run: rustup default nightly
       - run: rustup component add llvm-tools-preview
       - run: |
           cargo install cargo-llvm-cov || true
-          cargo llvm-cov \
-            --workspace\
-            --all-features \
-            --lcov \
-            --output-path coverage.lcov
+          cargo install grcov || true
+          ./coverage_report.sh
       # If using tarapulin
       #- run: cargo install cargo-tarpaulin
       #- run: cargo tarpaulin --out Xml
       - name: Upload coverage reports to Codecov
         uses: codecov/codecov-action@v5
         with:
-          files: ./coverage.lcov
+          files: ./target/grcov/lcov
           verbose: true