[Async] Multi Exec on cluster

[vladvildanov]

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Description of change

Async implementation of #3611

[Copilot]

Pull Request Overview

This PR introduces asynchronous support for cluster transactions, enhancing error handling during operations such as migrations and connection issues.

• Added comprehensive async tests for cluster transactions covering AskError, ExecAbortError, and connection errors.
• Updated behavior of the cluster pipeline tests by removing the deprecated transaction flag check.

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
tests/test_asyncio/test_cluster_transaction.py	Added extensive async transaction tests with various error cases.
tests/test_asyncio/test_cluster.py	Removed deprecated transaction check and adjusted the behavior.