Reduce ci matrix jobs

Author: kateinoigakukun

.github/workflows/test.yml

@@ -8,13 +8,20 @@ jobs:
     name: Build and Test
     strategy:
       matrix:
-        os: [macos-10.15, macos-11, macos-12, ubuntu-18.04, ubuntu-20.04]
-        toolchain:
-          - wasm-5.5.0-RELEASE
-          - wasm-5.6.0-RELEASE
-        wasi-backend:
-          - Node
-          - Wasmer
+        entry:
+          # Ensure that all host can install toolchain, build project, and run tests
+          - { os: macos-10.15,  toolchain: wasm-5.6.0-RELEASE, wasi-backend: Node }
+          - { os: macos-11,     toolchain: wasm-5.6.0-RELEASE, wasi-backend: Node }
+          - { os: macos-12,     toolchain: wasm-5.6.0-RELEASE, wasi-backend: Node }
+          - { os: ubuntu-18.04, toolchain: wasm-5.6.0-RELEASE, wasi-backend: Node }
+          - { os: ubuntu-20.04, toolchain: wasm-5.6.0-RELEASE, wasi-backend: Node }
+
+          # Ensure that test succeeds with all toolchains and wasi backend combinations
+          - { os: ubuntu-20.04, toolchain: wasm-5.5.0-RELEASE, wasi-backend: Node }
+          - { os: ubuntu-20.04, toolchain: wasm-5.6.0-RELEASE, wasi-backend: Node }
+          - { os: ubuntu-20.04, toolchain: wasm-5.5.0-RELEASE, wasi-backend: Wasmer }
+          - { os: ubuntu-20.04, toolchain: wasm-5.6.0-RELEASE, wasi-backend: Wasmer }
+
     runs-on: ${{ matrix.os }}
     steps:
       - name: Checkout