build: update tests workflow

- Update actions to their latest versions.
- Use SHA to (potentially) allow enabling Dependabot.
- Add Go Modules caching using  `actions/setup-go` (supported since
  >=v3).

Signed-off-by: Hidde Beydals <hidde@hhh.computer>

.github/workflows/tests.yaml

@@ -20,18 +20,14 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@24cb9080177205b6e8c946b17badbe402adc938f # v3.4.0
       - name: Setup Go
-        uses: actions/setup-go@v3
+        uses: actions/setup-go@4d34df0c2316fe8122ab82dc22947d607c0c91f9 # v4.0.0
         with:
           go-version: 1.20.x
-      - name: Restore Go cache
-        uses: actions/cache@v3
-        with:
-          path: /home/runner/work/_temp/_github_home/go/pkg/mod
-          key: ${{ runner.os }}-go-${{ hashFiles('**/go.sum') }}
-          restore-keys: |
-            ${{ runner.os }}-go-
+          cache-dependency-path: |
+            **/go.sum
+            **/go.mod
       - name: Run tests
         env:
           SKIP_COSIGN_VERIFICATION: true
@@ -45,11 +41,14 @@ jobs:
     runs-on: [self-hosted, Linux, ARM64, equinix]
     steps:
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@24cb9080177205b6e8c946b17badbe402adc938f # v3.4.0
       - name: Setup Go
-        uses: actions/setup-go@v3
+        uses: actions/setup-go@4d34df0c2316fe8122ab82dc22947d607c0c91f9 # v4.0.0
         with:
           go-version: 1.20.x
+          cache-dependency-path: |
+            **/go.sum
+            **/go.mod
       - name: Run tests
         env:
           SKIP_COSIGN_VERIFICATION: true
@@ -76,18 +75,14 @@ jobs:
     runs-on: ${{ matrix.os }}
     steps:
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@24cb9080177205b6e8c946b17badbe402adc938f # v3.4.0
       - name: Setup Go
-        uses: actions/setup-go@v3
+        uses: actions/setup-go@4d34df0c2316fe8122ab82dc22947d607c0c91f9 # v4.0.0
         with:
           go-version: 1.20.x
-      - name: Restore Go cache
-        uses: actions/cache@v3
-        with:
-          path: /home/runner/work/_temp/_github_home/go/pkg/mod
-          key: ${{ runner.os }}-go-${{ hashFiles('**/go.sum') }}
-          restore-keys: |
-            ${{ runner.os }}-go-
+          cache-dependency-path: |
+            **/go.sum
+            **/go.mod
       - name: Install and configure Docker using colima
         # Ref: https://github.com/abiosoft/colima/blob/main/docs/FAQ.md#cannot-connect-to-the-docker-daemon-at-unixvarrundockersock-is-the-docker-daemon-running
         run: |