Test wasm with pinned dependencies

So far testing was was done unpinned however that risked randomly
breaking builds whenever a dependency changes by accident. There was a
note explicitly acknowledging lack of pinning but with no explanation
why that was the case. So it might be because the author didn't want to
bother and pinning can be implemented.

Author: Kixunil

.github/workflows/rust.yml

@@ -258,12 +258,14 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       fail-fast: false
-      # Note we do not use the recent lock file for wasm testing.
     steps:
       - name: "Checkout repo"
         uses: actions/checkout@v4
       - name: "Select toolchain"
-        uses: dtolnay/rust-toolchain@stable
+        uses: dtolnay/[email protected]
+      - name: "Set dependencies"
+        # For now we only use msrv lock
+        run: cp Cargo-msrv.lock Cargo.lock
       - name: "Run wasm script"
         run: ./contrib/wasm.sh