Add Cargo.lock to canister test cache key (#867)

* Add Cargo.lock to canister test cache key

For unknown reasons, the Cargo.lock wasn't added to the cache key,
meaning that a Cargo.{lock,toml} update would not invalidate the cache.

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Co-authored-by: github-actions <41898282+github-actions[bot]@users.noreply.github.com>

.github/workflows/canister-tests.yml

@@ -179,10 +179,11 @@ jobs:
           # note on paths: we include the whole ~/.cargo/. (as opposed to juse .cargo/git, etc) because cargo stores crate
           # data as .crates(2?).{json,toml} without which the whole cache is invalidated. We may accumulate unnecessary
           # stuff but the cache is anyway invalidated on every toolchain update.
+          # We also include all Cargo tomls and the lockfile
           path: |
             ~/.cargo
             target
-          key: ${{ runner.os }}-cargo-${{ hashFiles('src/**/Cargo.lock', 'rust-toolchain.toml') }}-2
+          key: ${{ runner.os }}-cargo-${{ hashFiles('Cargo.lock', 'Cargo.toml', 'src/**/Cargo.toml', 'rust-toolchain.toml') }}-2
 
       - name: 'Download wasm'
         uses: actions/download-artifact@v2