fix: guard integration test resource names against 63-char API limit (#729)

## Summary

- Adds a 63-character API name limit guard to
`get_random_resource_name`, following the approach from
`apify-sdk-python`
- Fixes flaky `test_schedule_create_and_get[async]` caused by name
collisions with stale schedules from cancelled CI runs

## Failed CI runs

- https://github.com/apify/apify-client-python/actions/runs/24454251436/job/71450645691

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Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>