Implement retry logic with exponential backoff for connection errors

[blizard863]

Related to #19

This pull request introduces retry logic with exponential backoff for connection errors in both gssh_runner.go and nssh_runner.go files, enhancing the robustness of SSH tunnel connections. Additionally, it ensures proper handling of WaitGroup upon successful retries, maintaining the integrity of the running processes.

• Implements retry logic: Adds a retry mechanism for SSH tunnel connections in case of failures. This is done through a separate goroutine that attempts to reconnect with an exponential backoff strategy, starting from 1 second and doubling each time until it reaches a 30-second interval.
• Handles WaitGroup upon successful retry: Ensures that the WaitGroup is correctly managed upon a successful retry, preventing premature exit of the Run function and maintaining the stability of the application.
• Enhances error logging: Improves error logging for both initial connection failures and subsequent retry attempts, providing better visibility into the connection process and potential issues.

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