ci: add wasm32v1-none target and SKIP_WASM_BUILD to fix serde_core duplicate alloc error

The paritytech CI container lacks the wasm32v1-none target, causing
wasm-builder to fall back to wasm32-unknown-unknown with -Z build-std.
Combined with our serde_core fork, this creates a duplicate lang item
error for alloc crate.

Fix: Add rustup target add wasm32v1-none to all WASM-building jobs.
For check-only jobs (bench checks, docs, each-crate), add SKIP_WASM_BUILD=1.

Also fixes test-deterministic-wasm wasm blob path to work with either target.

.github/workflows/tests.yml

@@ -36,6 +36,9 @@ jobs:
       - name: Checkout
         uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0
 
+      - name: Install wasm32v1-none target
+        run: rustup target add wasm32v1-none
+
       - name: Rust Cache
         uses: Swatinem/rust-cache@9d47c6ad4b02e050fd481d890b2ea34778fd09d6 # v2.7.8
         with:
@@ -57,6 +60,8 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0
+      - name: Install wasm32v1-none target
+        run: rustup target add wasm32v1-none
       - name: script
         id: test
         run: |
@@ -77,6 +82,7 @@ jobs:
     container:
       image: ${{ needs.preflight.outputs.IMAGE }}
     env:
+      SKIP_WASM_BUILD: 1
       CARGO_INCREMENTAL: 0
     steps:
       - name: Checkout
@@ -90,4 +96,4 @@ jobs:
 
       - name: script
         run: |
-          cargo check --workspace --benches --features runtime-benchmarks --quiet
+          cargo check --workspace --locked --benches --features runtime-benchmarks --quiet