workflows: merge lints together

They share the same branch and pull request settings. Also makes the
GitHub commit status context used more consistent between the two.
Currently one is "golangci-lint/lint" and the other "lints/ShellCheck".
With this, it'll be "lints/golangci-lint" and "lints/ShellCheck".

.github/workflows/lints.yml

@@ -22,3 +22,32 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@v2
       - run: make shellcheck
+  golangci-lint:
+    name: golangci-lint
+    runs-on: ubuntu-latest
+    steps:
+      # this is needed by containers/storage which we're using in gangplank
+      - name: Install deps
+        run: sudo apt-get install -y libgpgme-dev libbtrfs-dev libdevmapper-dev
+      - uses: actions/setup-go@v3
+        with:
+          go-version: 1.18
+      - uses: actions/checkout@v3
+      - name: golangci-lint
+        uses: golangci/golangci-lint-action@v3
+        with:
+          version: v1.46.2
+          working-directory: gangplank
+          args: --timeout=5m
+      - name: golangci-lint
+        uses: golangci/golangci-lint-action@v3
+        with:
+          version: v1.46.2
+          working-directory: mantle
+          args: --timeout=5m
+      - name: golangci-lint
+        uses: golangci/golangci-lint-action@v3
+        with:
+          version: v1.46.2
+          working-directory: schema
+          args: --timeout=5m