VaadinDevmodeGizmo duplicates messages when dismissed permanently

[mshabarov]

Description of the bug / feature

When the VaadinDevmodeGizmo is chosen to not be shown again and dismissed, the warning messages are always added to a list, bloating the message log:

Ideally, the message has a flag of "repeatability", and gizmo duplicates the message depending of that flag. That can show multiple messages when its worth and a single message, e.g. as in case with PreserveOnRefresh.

Minimal reproducible example

skeleton-starter-flow-spring-preserve.zip

1. Open and run the project.
2. Go to http://localhost:8080
3. Click Don't show again and then Dismiss in the gizmo popup
4. Navigate to the child view by clicking on the navigate button
5. Navigate back to the main view
6. Notice that there are so many dev mode gizmo messages as many times you navigate to main view.

Expected behavior

Single VaadinDevmodeGizmo message

Actual behavior

Multiple VaadinDevmodeGizmo messages

Versions:

• Vaadin / Flow version: 21.0.0.alpha2 / 8.0.0.alpha3
• Java version: 15
• OS version: Mac OS
• Browser version (if applicable): Chrome 90
• Application Server (if applicable): spring-boot
• IDE (if applicable): IntelliJ IDEA Ultimate