Added support for the skipMarkingStageUnstable config option

[arnaudsjs]

This PR adds the skipMarkingStageUnstable configuration option. If checked, a failed test will not mark the the node, stage or build as unstable.

Closes #1238

Testing done

The test suite was extended with automated tests.

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[Copilot]

Pull request overview

Adds a new Pipeline junit step option, skipMarkingStageUnstable, to prevent attaching a WarningAction when tests fail so that stages (and consequently builds) are not marked UNSTABLE while still recording test results—addressing #1238.

Changes:

• Added skipMarkingStageUnstable to JUnitResultsStep and applied it in JUnitResultsStepExecution to skip WarningAction (and build result mutation) on test failures.
• Extended Pipeline step tests to cover the new behavior.
• Documented the new option across help and README, and clarified interaction with skipMarkingBuildUnstable.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/test/java/hudson/tasks/junit/pipeline/JUnitResultsStepTest.java	Adds a Pipeline test ensuring failures don’t attach WarningAction when skipMarkingStageUnstable is enabled.
src/main/resources/hudson/tasks/junit/pipeline/JUnitResultsStep/help-skipMarkingStageUnstable.html	New help content documenting the new option and its effect.
src/main/resources/hudson/tasks/junit/pipeline/JUnitResultsStep/help-skipMarkingBuildUnstable.html	Updates help text to clarify interaction with skipMarkingStageUnstable.
src/main/resources/hudson/tasks/junit/pipeline/JUnitResultsStep/config.jelly	Adds the new checkbox to the Pipeline step configuration UI.
src/main/java/hudson/tasks/junit/pipeline/JUnitResultsStepExecution.java	Implements the behavior change: skips WarningAction and build UNSTABLE marking when configured.
src/main/java/hudson/tasks/junit/pipeline/JUnitResultsStep.java	Adds the new DataBound option (skipMarkingStageUnstable).
README.md	Documents the new option and clarifies semantics vs skipMarkingBuildUnstable.

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[timja]

LGTM