refactor: Move batch service tests and enrich docstrings

Moves tests for the batch service from  to  to better align with the new module structure. Deletes the now-redundant .

Also enriches docstrings across the batch module, including , , , and , to improve code clarity and explain the security model of using GCP Batch for isolated task execution.

Fixes all related linting errors and ensures all tests continue to pass.

Author: javanlacerda

src/clusterfuzz/_internal/batch/gcp.py

@@ -91,10 +91,10 @@ def _get_task_spec(batch_workload_spec):
 def _set_preemptible(instance_policy, batch_workload_spec) -> None:
   if batch_workload_spec.preemptible:
     instance_policy.provisioning_model = (
-        batch.AllocationPolicy.Provisioning_model.PREEMPTIBLE)
+        batch.AllocationPolicy.ProvisioningModel.PREEMPTIBLE)
   else:
     instance_policy.provisioning_model = (
-        batch.AllocationPolicy.Provisioning_model.STANDARD)
+        batch.AllocationPolicy.ProvisioningModel.STANDARD)
 
 
 def _get_allocation_policy(spec):

src/clusterfuzz/_internal/remote_task/__init__.py

@@ -1,4 +1,4 @@
-# Copyright 2023 Google LLC
+# Copyright 2025 Google LLC
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.