Regenerate the remote file upload proto to include TestSteps.

[ian-sift]

Tested uploading to a local report's step:

report = client.test_results.get(test_report_id="206e5580-7794-4b90-8800-79cb43656614")

steps = client.test_results.list_steps(test_reports=[report])

upload_step = steps[0]

readme = pathlib.Path("README.md")
upload_step.upload_attachment(path=readme, description="Test attachment")

[nathan-sift]

lgtm