Implement test server support for sync Nexus operation commands

[pdoerner]

What was changed

Added test server support for Nexus operation commands, including sync completion, timeouts, failures, and retries. Added most of the stubs for implementing asynchronous operations in followup PRs.

The test server will only support worker targets, not external, so there is no added logic for making HTTP requests.
The implementation largely follows the same design as ActivityTasks.

[pdoerner]

I know these tests have a lot of copy-pasted code; didn't want to spend a ton of time on test design in this PR. Planning to add more coverage and refactor common code when writing async operation tests.

[Quinn-With-Two-Ns]

Does the real server also throw an INTERNAL error if the task token is bad?

[Quinn-With-Two-Ns]

If this was the core Java SDK I would probably advocate for doing the try catch to a GRPC specific exception outside of toBytes to separate the transport details from the implementation. For the test server it is fine.

[pdoerner]

Ah good catch, it throws INVALID_ARGUMENT; I'll update.

[pdoerner]

Actually I think serialization error is INTERNAL and deserialization is INVALID_ARGUMENT so that's what I've changed it to.

[Quinn-With-Two-Ns]

LGTM, nothing stands out as obviously wrong, but I'll admit I don't know how the nexus task state machine on the server looks and if it matches the test server. Relying on the tests to ensure we have very close behaviour here.

[Quinn-With-Two-Ns]

This Test test failure here looks problematic, seems like an upsert search attribute test was treated as a nexus operation

    event_id: 4
    event_time { seconds: 1723665245 nanos: 673000000 }
    event_type: EVENT_TYPE_WORKFLOW_TASK_FAILED
    workflow_task_failed_event_attributes { 
      scheduled_event_id: 2
      started_event_id: 3
      cause: WORKFLOW_TASK_FAILED_CAUSE_BAD_SCHEDULE_NEXUS_OPERATION_ATTRIBUTES
      failure { message: "BadScheduleNexusOperationAttributes: Could not find Nexus endpoint with name: " source: "JavaSDK" stack_trace: "io.temporal.internal.testservice.CommandVerifier.verifyCommand(CommandVerifier.java:69)\nio.temporal.internal.testservice.TestWorkflowMutableStateImpl.lambda$completeWorkflowTask$4(TestWorkflowMutableStateImpl.java:439)\nio.temporal.internal.testservice.TestWorkflowMutableStateImpl.update(TestWorkflowMutableStateImpl.java:285)\nio.temporal.internal.testservice.TestWorkflowMutableStateImpl.completeWorkflowTaskUpdate(TestWorkflowMutableStateImpl.java:263)\nio.temporal.internal.testservice.TestWorkflowMutableStateImpl.completeWorkflowTask(TestWorkflowMutableStateImpl.java:387)\nio.temporal.internal.testservice.TestWorkflowService.respondWorkflowTaskCompleted(TestWorkflowService.java:501)\nio.temporal.api.workflowservice.v1.WorkflowServiceGrpc$MethodHandlers.invoke(WorkflowServiceGrpc.java:6057)\nio.grpc.stub.ServerCalls$UnaryServerCallHandler$UnaryServerCallListener.onHalfClose(ServerCalls.java:182)\nio.grpc.internal.ServerCallImpl$ServerStreamListenerImpl.halfClosed(ServerCallImpl.java:355)\nio.grpc.internal.ServerImpl$JumpToApplicationThreadServerStreamListener$1HalfClosed.runInContext(ServerImpl.java:867)\nio.grpc.internal.ContextRunnable.run(ContextRunnable.java:37)\nio.grpc.internal.SerializingExecutor.run(SerializingExecutor.java:133)\njava.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144)\njava.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642)\njava.base/java.lang.Thread.run(Thread.java:1589)\n" server_failure_info { non_retryable: true } }
      identity: "25083@fv-az695-304"
    }