Add codecov to Go unit tests (#282)

Adds code coverage to Go unit tests.

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **Chores**
* Integrated automated unit test coverage reporting with Codecov
integration
* Restructured test execution to separate unit and end-to-end tests into
distinct workflows

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

.github/workflows/go.yaml

@@ -33,8 +33,13 @@ jobs:
         run: |
           make -B generate
           git diff --exit-code
-      - name: Running unit tests
-        run: make test
+      - name: Run unit tests
+        run: make test-unit
+      - name: Upload coverage reports to Codecov
+        uses: codecov/codecov-action@e79a6962e0d4c0c17b229090214935d2e33f8354 #v6.0.1
+        with:
+          token: ${{ secrets.CODECOV_TOKEN }}
+          flags: unit
   e2e:
     runs-on: ubuntu-latest
     steps:
@@ -44,5 +49,5 @@ jobs:
         uses: actions/setup-go@4a3601121dd01d1626a1e23e37211e3254c1c06c #v6.4.0
         with:
           go-version-file: go.mod
-      - name: Running e2e tests
-        run: make test-e2e
+      - name: Run e2e tests
+        run: make -B test-e2e