Add deep links tool window integration test

[helin24]

This opens a project and checks that the deep links panel can be opened (since it does not require a running app).

I'm able to run on mac with ./gradlew integration --tests "io.flutter.integrationTest.DeepLinksToolWindowTest". Sometimes I've gotten weird errors when I don't run ./gradlew clean first, but not always.

Part of #7959

[gemini-code-assist]

Code Review

This pull request adds an integration test for the Deep Links tool window. The test creates a new Flutter project, opens it in the IDE, and verifies that the Deep Links tool window can be opened and contains a browser component.

My review has identified a few areas for improvement:

• The test has some state management and cleanup issues that could affect test isolation and cause resource leaks.
• The test uses println for logging, which is against the repository's style guide.
• There are some minor import cleanup opportunities.

Please see the detailed comments for suggestions.

[helin24]

@gemini-code-assist can you review again?

[gemini-code-assist]

Code Review

This pull request adds a new integration test for the Deep Links tool window. The test correctly creates a project, opens the IDE, and verifies that the tool window can be opened. My feedback includes suggestions to replace println calls with a proper logger as required by the style guide, and to use a predefined constant for the tool window ID to improve maintainability.