[Misc] Batch: Extend batch session retry handling with capped backoff to support more retry times.

[zhangjyr]

Pull Request Description

• make batch session retry attempts configurable via AIBRIX_BATCH_SESSION_RETRY_ATTEMPTS
• cap runtime session retry backoff at 60 seconds
• annotate exhausted session errors with retry and attempt counts
• add tests for env wiring, capped delays, and exhausted retry behavior

Related Issues

Resolves: #[Insert issue number(s)]

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[gemini-code-assist]

Code Review

This pull request introduces configurable session retry attempts via environment variables, caps the maximum retry delay at 60 seconds, and appends retry and attempt details to exceptions when session retries are exhausted. The feedback highlights three key areas for improvement: first, updating the custom __deepcopy__ methods of specific exceptions to ensure the appended retry suffix is not lost during deep copies; second, capping the attempt count to prevent potential OverflowError during exponential backoff calculation; and third, mutating the exception in-place before using a bare raise to preserve the original traceback.