issue #7245 : show unit test variables in pipeline run dialog

[mattcasters]

What changes were proposed in this pull request?

When a pipeline unit test is selected in Hop GUI, its configured variables are now pre-loaded into the Variables (and Parameters) tabs of the pipeline execution dialog so the user can review and change them before running.

Details

• Move HopGuiPipelineExecutionConfiguration in HopGuiPipelineRunDelegate.executePipeline() to before the run configuration dialog (matching the extension point description).
• Add HopGuiUnitTestVariablesExtensionPoint in the testing plugin to copy active unit-test variables into the execution configuration.
• Parameter-named unit-test entries go into the parameters map; others into the variables map.
• Keys/values are resolved against the current variables; unit-test values override existing map entries.

What was tested?

• Manual: select a unit test with variables, open Launch — variables appear on the Variables tab.
• Unit tests: HopGuiUnitTestVariablesExtensionPointTest (6 tests)

How can this be tested?

1. Open a pipeline that has a unit test with variables defined.
2. Select that unit test in the toolbar.
3. Run / Launch the pipeline.
4. Confirm the unit test variables appear on the Variables tab (and parameter-named ones on Parameters).
5. Change a value and launch — confirm the edited value is used for that run.

Fixes: #7245