GitHub Actions: Add mypy problem matcher (#37485)

.github/workflows/ci.yaml

@@ -669,6 +669,9 @@ jobs:
         run: |
           echo "Failed to restore Python virtual environment from cache"
           exit 1
+      - name: Register mypy problem matcher
+        run: |
+          echo "::add-matcher::.github/workflows/matchers/mypy.json"
       - name: Run mypy
         run: |
           . venv/bin/activate

.github/workflows/matchers/mypy.json

+{
+  "problemMatcher": [
+    {
+      "owner": "mypy",
+      "pattern": [
+        {
+          "regexp": "^(.+):(\\d+):\\s(error|warning):\\s(.+)$",
+          "file": 1,
+          "line": 2,
+          "severity": 3,
+          "message": 4
+        }
+      ]
+    }
+  ]
+}