RFR: 8316017: Refactor timeout handler in PassFailJFrame [v2]

[Alexey Ivanov]

> 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.

Alexey Ivanov has updated the pull request incrementally with one additional commit since the last revision:

  Refactor failure reason
  
  Ensure the failure reason doesn't change after it's set.
  Removed 'failed' and 'timeout' fields:
  if failureReason is set, the test fails.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/15668/files
  - new: https://git.openjdk.org/jdk/pull/15668/files/27f39736..39ebc7c8

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15668&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15668&range=00-01

  Stats: 79 lines in 1 file changed: 47 ins; 15 del; 17 mod
  Patch: https://git.openjdk.org/jdk/pull/15668.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15668/head:pull/15668

PR: https://git.openjdk.org/jdk/pull/15668