Fetch paginated cloud execution history

[zhongkechen]

Summary

• Follow NextMarker in DurableFunctionCloudTestRunner history fetches and merge all pages before building results
• Add paginated cloud-runner coverage for callbacks, wait_for_result, steps, and child contexts
• Add a many-operations example with top-level steps and child-context steps

Fixes: #510

Tests

• hatch run test:all packages/aws-durable-execution-sdk-python-testing/tests/runner_test.py packages/aws-durable-execution-sdk-python-examples/test/comprehensive_operations
• hatch fmt --check
• hatch run types:check packages/aws-durable-execution-sdk-python-testing/src/aws_durable_execution_sdk_python_testing/runner.py packages/aws-durable-execution-sdk-python-testing/tests/runner_test.py packages/aws-durable-execution-sdk-python-examples/src/comprehensive_operations/many_operations.py packages/aws-durable-execution-sdk-python-examples/test/comprehensive_operations/test_many_operations.py

[zhongkechen]

CI failed due to #503

[yaythomas]

adds this support to locarunner: #515