workflows: update to run unit tests in GitHub Actions job

Epic: CRDB-8308
Release note: None

.github/workflows/experimental-github-actions-testing.yml

@@ -7,4 +7,13 @@ jobs:
   test_job:
     runs-on: [self-hosted, basic_runner_group]
     steps:
-      - run: echo hi
+      - uses: actions/checkout@v4
+        with:
+          # By default, checkout merges the PR into the current master.
+          # Instead, we want to check out the PR as is.
+          ref: ${{ github.event.pull_request.head.sha }}
+      - run: ./build/github/get-engflow-keys.sh
+      - run: bazel test //pkg:all_tests --config engflowpublic --config crosslinux --jobs 300 --tls_client_certificate=/home/agent/engflow.crt --tls_client_key=/home/agent/engflow.key --remote_download_minimal
+      - name: clean up
+        if: always()
+        run: rm -f /home/agent/engflow.*

build/github/get-engflow-keys.sh

@@ -0,0 +1,6 @@
+#!/usr/bin/env bash
+
+set -euxo pipefail
+
+gcloud secrets versions access 1 --secret=engflow-mesolite-key > /home/agent/engflow.key
+gcloud secrets versions access 1 --secret=engflow-mesolite-crt > /home/agent/engflow.crt