workflows: add separate job for coverage

Otherwise each of our test jobs uploads coverage profile to Codecov which
make zero sense and actually can lead to misleading results.

Signed-off-by: Roman Khimov <roman@nspcc.ru>

.github/workflows/go.yml

@@ -42,6 +42,9 @@ jobs:
             go: '1.20'
           - os: macos-14
             go: '1.21'
+          # Exclude latest Go version for Ubuntu as Coverage uses it.
+          - os: ubuntu-latest
+            go: '1.22'
     steps:
 
     - name: Setup go
@@ -53,6 +56,22 @@ jobs:
       uses: actions/checkout@v4
 
     - name: Tests
+      run: go test -race ./...
+
+  test:
+    name: Coverage
+    runs-on: ubuntu-latest
+    steps:
+
+    - name: Setup Go
+      uses: actions/setup-go@v5
+      with:
+        go-version: 1.22
+
+    - name: Check out
+      uses: actions/checkout@v4
+
+    - name: Collect coverage
       run: go test -coverprofile=coverage.txt -covermode=atomic ./...
 
     - name: Upload coverage results to Codecov