Add verification that files are opened in the editor after clicking in project tree

[SkorikSergey]

What does this PR do?

When clicking on a file in the Project Explorer to open it, sometimes the file doesn't actually open in the Editor - especially after closing the Trust Author dialog. Tests would proceed without verifying the file was opened, leading to failures in subsequent steps that depend on the file being open.

Solution
Added openFileAndVerify() method to ProjectAndFileTests.ts that:

• Opens a file using projectSection.openItem()
• Verifies the file appears in the editor tabs using EditorView.getOpenEditorTitles()
• Retries up to 2 times if the file doesn't open on the first attempt
• Throws a descriptive error if all attempts fail

Benefits

• Ensures file is actually opened before proceeding with test actions
• Provides retry mechanism for flaky file opening after dialogs
• Reusable method available for other tests that need to open files

Screenshot/screencast of this PR

What issues does this PR fix or reference?

https://issues.redhat.com/browse/CRW-10220

How to test this PR?

PR Checklist

As the author of this Pull Request I made sure that:

• The Eclipse Contributor Agreement is valid
• Code produced is complete
• Code builds without errors
• Tests are covering the bugfix or new feature
• The repository devfile is up to date and works
• Sections What issues does this PR fix or reference and How to test this PR completed
• Relevant user documentation updated
• Relevant contributing documentation updated
• CI/CD changes implemented, documented and communicated

Reviewers

Reviewers, please comment how you tested the PR when approving it.

[artaleks9]

IMHO, PR looks good, can be merged.
Just to clarify: was there a launch the E2E test with these changes ?

[SkorikSergey]

IMHO, PR looks good, can be merged. Just to clarify: was there a launch the E2E test with these changes ?

@artaleks9 thank you for review. I tested these changes several times on DS 3.26.0 from my laptop.

[dmytro-ndp]

Functional-tests pipeline run didn't show regression.

ExtensionActivationTest test has passed.

Well done, @SkorikSergey