RFR: 8316017: Refactor timeout handler in PassFailJFrame

[lawrence.andrews]

On Mon, 11 Sep 2023 18:18:28 GMT, Alexey Ivanov <aivanov at openjdk.org> wrote:

> Refactored timeout handling in PassFailJFrame:
> 
> 1. Managing the timer and formatting the time left is inside `TimeoutHandler` class.
> 2. The class handles timer events and updates the label accordingly.
> 
> This is implemented on top of #15665.

Looks good to me.

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PR Comment: https://git.openjdk.org/jdk/pull/15668#issuecomment-1714800439