exstore/pipeline integration

[cconstable]

Client + Nexus + Worker external storage integration

What was changed

• enabled extstore via WorkflowClientOptions.setExternalStorage(...), worker/WorkerFactoryOptions, internal/worker/SingleWorkerOptions, and worker/Worker
• client/worker with no external storage configured fails with TMPRL-1105
• Client: integration via new decorator ExternalStorageGenericWorkflowClient that is used in client/WorkflowClientInternalImpl
• Workers: integration via internal/worker/{WorkflowWorker,ActivityWorker,NexusWorker} and internal/replay/{ServiceWorkflowHistoryIterator,ReplayWorkflowTaskHandler}
• Activity completion + heartbeat integration.

Why?

• makes extstore "work"

Checklist

• ExternalStoragePipelineTest and ExternalStorageReferenceGuardTest