Restructure GH tests, run on u64 & u32

.github/workflows/main.yml

@@ -5,8 +5,57 @@ on:
     types: [opened, repoened, synchronize]
 
 jobs:
-  combo:
-    name: test + Clippy + rustfmt
+  test:
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        backend_feature:
+          - u64_backend
+          - u32_backend
+    name: test
+    steps:
+      - name: Checkout sources
+        uses: actions/checkout@v2
+
+      - name: Install nightly toolchain
+        uses: actions-rs/toolchain@v1
+        with:
+          profile: minimal
+          toolchain: nightly
+          override: true
+          components: rustfmt, clippy
+
+      - name: Run cargo test
+        uses: actions-rs/cargo@v1
+        with:
+          command: test
+          args: --no-default-features --features ${{ matrix.backend_feature }}
+
+  clippy:
+    name: cargo clippy
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout sources
+        uses: actions/checkout@v2
+
+      - name: Install nightly toolchain
+        uses: actions-rs/toolchain@v1
+        with:
+          profile: minimal
+          toolchain: nightly
+          override: true
+          components: rustfmt, clippy
+
+      - name: Run cargo clippy
+        uses: actions-rs/cargo@v1
+        with:
+          command: clippy
+          args: -- -D warnings
+
+
+  format:
+    name: cargo fmt
     runs-on: ubuntu-latest
     steps:
       - name: Checkout sources
@@ -26,18 +75,6 @@ jobs:
           command: fmt
           args: --all -- --check
 
-      - name: Run cargo clippy
-        uses: actions-rs/cargo@v1
-        with:
-          command: clippy
-          args: --all-features -- -D warnings
-
-      - name: Run cargo test
-        uses: actions-rs/cargo@v1
-        with:
-          command: test
-          args: --all-features
-
   deny-check:
     name: cargo-deny check
     runs-on: ubuntu-latest