fix: Round 10 - Use official setup-envtest tool for Kubernetes test environment

The manual kubebuilder tools download was failing because the file
doesn't exist at the assumed URL. The official approach is to use
the setup-envtest tool from controller-runtime/tools.

Changes:
- Install setup-envtest using `go install`
- Use setup-envtest to download and configure test binaries
- Automatically sets KUBEBUILDER_ASSETS to the correct path
- Removes manual tar extraction and URL guessing

This is the recommended approach per kubebuilder documentation:
https://book.kubebuilder.io/reference/envtest.html

Files modified:
- .github/workflows/test.yml (lines 175-188)
- .github/workflows/reusable/build-test.yml (lines 85-98)

Related: #CI-fixes

Author: thc1006

.github/workflows/reusable/build-test.yml

@@ -87,13 +87,14 @@ jobs:
       run: |
         echo "Setting up test environment for ${{ inputs.test-type }} tests..."
 
-        # Download and extract kubebuilder test binaries
-        # Use direct GCS URL to avoid redirect issues
-        curl -sSLo envtest-bins.tar.gz "https://storage.googleapis.com/kubebuilder-tools/kubebuilder-tools-1.31.1-linux-amd64.tar.gz"
-        mkdir -p /tmp/kubebuilder/bin
-        tar -C /tmp/kubebuilder --strip-components=1 -xzf envtest-bins.tar.gz
+        # Install setup-envtest tool
+        go install sigs.k8s.io/controller-runtime/tools/setup-envtest@latest
 
-        echo "KUBEBUILDER_ASSETS=/tmp/kubebuilder/bin" >> $GITHUB_ENV
+        # Download and setup envtest binaries using official tool
+        ENVTEST_K8S_VERSION=1.31.1 setup-envtest use -p env
+
+        # Export assets path
+        echo "KUBEBUILDER_ASSETS=$(setup-envtest use -i -p path 1.31.1)" >> $GITHUB_ENV
         echo "USE_EXISTING_CLUSTER=false" >> $GITHUB_ENV
 
     - name: Validate component path

.github/workflows/test.yml

@@ -177,20 +177,15 @@ jobs:
       run: |
         echo "Setting up Kubernetes test environment for ${{ matrix.component.name }}"
 
-        # Download and extract kubebuilder binaries
-        # Use direct GCS URL to avoid redirect issues
-        curl -sSLo envtest-bins.tar.gz "https://storage.googleapis.com/kubebuilder-tools/kubebuilder-tools-${{ env.K8S_VERSION }}-linux-amd64.tar.gz"
-        mkdir -p /tmp/kubebuilder/bin
-        tar -C /tmp/kubebuilder --strip-components=1 -xzf envtest-bins.tar.gz
-
-        # Set environment variables
-        echo "KUBEBUILDER_ASSETS=/tmp/kubebuilder/bin" >> $GITHUB_ENV
-        echo "USE_EXISTING_CLUSTER=false" >> $GITHUB_ENV
+        # Install setup-envtest tool
+        go install sigs.k8s.io/controller-runtime/tools/setup-envtest@latest
+
+        # Download and setup envtest binaries using official tool
+        ENVTEST_K8S_VERSION=${{ env.K8S_VERSION }} setup-envtest use -p env
 
-        # Verify installation
-        ls -la /tmp/kubebuilder/bin/
-        /tmp/kubebuilder/bin/etcd --version
-        /tmp/kubebuilder/bin/kube-apiserver --version
+        # Export assets path
+        echo "KUBEBUILDER_ASSETS=$(setup-envtest use -i -p path ${{ env.K8S_VERSION }})" >> $GITHUB_ENV
+        echo "USE_EXISTING_CLUSTER=false" >> $GITHUB_ENV
 
     - name: Cache dependencies
       uses: actions/cache@v4