fix(ci): restore wasm32v1-none target and remove WASM_BUILD_STD=0

The WASM_BUILD_STD=0 approach caused panic_impl duplicate errors because
wasm32-unknown-unknown pre-built sysroot includes std, conflicting with
pezsp-io's panic handler in wasm runtime builds.

Local testing confirmed that wasm32v1-none + no build-std + serde fork
works correctly. The wasm-builder creates a separate cargo project that:
- Excludes std/default features from the runtime
- Has no client crates in the dependency tree
- Properly uses the serde fork for target_os="none" handling

Restore rustup target add wasm32v1-none in all 14 CI build jobs and
remove all WASM_BUILD_STD=0 overrides.

.github/workflows/tests.yml

@@ -42,9 +42,10 @@ jobs:
           shared-key: quick-benchmarks
           cache-on-failure: true
 
+      - name: Install wasm32v1-none target
+        run: rustup target add wasm32v1-none
+
       - name: script
-        env:
-          WASM_BUILD_STD: "0"
         run: cargo run --locked --release -p pezstaging-node-cli --bin bizinikiwi-node --features runtime-benchmarks --quiet -- benchmark pezpallet --chain dev --pezpallet "*" --extrinsic "*" --steps 2 --repeat 1 --quiet
 
   # cf https://github.com/pezkuwichain/pezkuwi-sdk/issues/1652