re-add helm unit test with checksum pin

.github/workflows/helm_unit_test.yml

@@ -0,0 +1,36 @@
+name: Helm unit test
+
+on:
+  pull_request:
+  push:
+    branches:
+      - main
+
+jobs:
+  unit-test:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@08eba0b27e820071cde6df949e0beb9ba4906955 # v4.3.0
+
+      - name: Set up Helm 3.11.1
+        uses: azure/setup-helm@1a275c3b69536ee54be43f2070a358922e12c8d4 # v4.3.1
+        with:
+          version: "3.11.1"
+
+      - name: Install Helm Unit Test Plugin
+        run: |
+          helm plugin install https://github.com/helm-unittest/helm-unittest --version v0.4.4
+      - name: Verify Helm Unit Test Plugin integrity
+        run: |
+          EXPECTED_SHA="e251ba198448629678ff2168e1a469249d998155"
+          PLUGIN_DIR="$(helm env HELM_PLUGINS)/helm-unittest"
+          ACTUAL_SHA="$(git -C "$PLUGIN_DIR" rev-parse HEAD)"
+          if [ "$ACTUAL_SHA" != "$EXPECTED_SHA" ]; then
+            echo "::error::Helm unittest plugin checksum mismatch! Expected $EXPECTED_SHA but got $ACTUAL_SHA"
+            exit 1
+          fi
+          echo "Helm unittest plugin integrity verified: $ACTUAL_SHA"
+
+      - name: Run unit tests
+        run: helm unittest -f 'tests/*.yaml' deploy/charts/litellm-helm