e2e: Add Client Intro test framework and initial test. (#26639)

The new client intro test mimics the Consul and Vault compat tests
and uses local agents to perform the required setup. This method
allows us the flexibility moving forward to test when enforcement
mode is in strict.

The test suite will now be triggered from the test-e2e CI run
and can also be called by a make target.

.github/workflows/test-e2e.yml

@@ -82,10 +82,28 @@ jobs:
           sudo sed -i 's!Defaults!#Defaults!g' /etc/sudoers
           sudo -E env "PATH=$PATH" make integration-test-consul
 
+  test-e2e-client-intro:
+    runs-on: ${{ endsWith(github.repository, '-enterprise') && fromJSON('["self-hosted", "ondemand", "linux"]') || 'ubuntu-22.04' }}
+    steps:
+      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
+      - name: Git config token
+        if: endsWith(github.repository, '-enterprise')
+        run: git config --global url.'https://${{ secrets.ELEVATED_GITHUB_TOKEN }}@github.com'.insteadOf 'https://github.com'
+      - uses: actions/setup-go@f111f3307d8850f501ac008e886eec1fd1932a34 # v5.3.0
+        with:
+          cache: ${{ contains(runner.name, 'Github Actions') }}
+          go-version-file: .go-version
+          cache-dependency-path: "**/go.sum"
+      - name: Client Introuction
+        run: |
+          make deps
+          make integration-test-client-intro
+
   handle-failure:
     needs:
       - test-e2e-vault
       - test-e2e-consul
+      - test-e2e-client-intro
     if: always() && github.event_name == 'push' && contains(needs.*.result, 'failure')
     uses: ./.github/workflows/test-failure-notification.yml
     secrets: inherit