Add an "Open in the Browser" action when DevTools is in embedded mode

This button would allow a user to easily open DevTools in the browser when they are using an embedded DevTools tool in the IDE.

See https://github.com/flutter/flutter-intellij/issues/7839#issuecomment-2513087717 for more context.

No files, tests, or entry points are named. Start by reviewing the embedded DevTools integration and the linked flutter-intellij discussion to identify where actions are defined; done means an embedded-mode user can select the action and open DevTools in the browser.

Written by the indexing model from the issue text.