Add retry utility snippet

[iluwatar]

Description:

Create a utility that retries execution of a Callable up to a defined number of times, with a delay between attempts. Useful for network and file operations.

Acceptance Criteria:

• A new retry snippet has been added
• Method retry(Callable task, int maxAttempts, long delayMillis) is implemented
• Retries task on failure with optional delay
• Test case showcases retrying on failure

[juhno1023]

Hi @iluwatar,
I’m interested in working on this issue as my first contribution.
Could you please assign it to me? Let me know if there’s anything I should be aware of before starting.