e2e: Continuous rolling-update of runners while workflow jobs are running

This should help revealing issues like https://github.com/actions-runner-controller/actions-runner-controller/issues/1535 if any.

acceptance/testdata/runnerdeploy.envsubst.yaml

@@ -49,6 +49,10 @@ spec:
       labels:
       - "${RUNNER_LABEL}"
 
+      env:
+      - name: ROLLING_UPDATE_PHASE
+        value: "${ROLLING_UPDATE_PHASE}"
+
       #
       # Non-standard working directory
       #

acceptance/testdata/runnerset.envsubst.yaml

@@ -121,6 +121,8 @@ spec:
           value: "${RUNNER_FEATURE_FLAG_EPHEMERAL}"
         - name: GOMODCACHE
           value: "/home/runner/.cache/go-mod"
+        - name: ROLLING_UPDATE_PHASE
+          value: "${ROLLING_UPDATE_PHASE}"
         # PV-backed runner work dir
         volumeMounts:
         # Comment out the ephemeral work volume if you're going to test the kubernetes container mode