Expose max-lag-secs for act benchmark.
Expose max-lag-secs for act benchmark.

PiperOrigin-RevId: 469897075

GoogleCloudPlatform/PerfKitBenchmarker,GoogleCloudPlatform/PerfKitBenchmarker,GoogleCloudPlatform/PerfKitBenchmarker,GoogleCloudPlatform/PerfKitBenchmarker