RFR: 8355515: Clarify the purpose of forcePass() and forceFail() methods

[Manukumar V S]

Clarified the purpose of forcePass() and forceFail() methods and recommended usage of these methods.

forcePass() contained an incorrect sample; it's addressed by [JDK-8355441](https://bugs.openjdk.org/browse/JDK-8355441).

The description of forceFail() has been expanded, too.


A new section in the description of the PassFailJFrame added to describe forcePass() and forceFail().

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Commit messages:
 - 8355515: Clarify the purpose of forcePass() and forceFail() methods

Changes: https://git.openjdk.org/jdk/pull/25091/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25091&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8355515
  Stats: 31 lines in 1 file changed: 29 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/25091.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25091/head:pull/25091

PR: https://git.openjdk.org/jdk/pull/25091