Fix incorrect usage of WidgetFlutterBindings.ensureInitialized()

[matux]

Description of the change

Fixes some deprecation issues, and an incorrect usage of WidgetFlutterBindings.ensureInitialized() on Flutter 3.10.x:

The Flutter bindings were initialized in a different zone than is now being used. This will likely cause confusion and bugs as any zone-specific configuration will inconsistently use the configuration of the original binding initialization zone or this zone based on hard-to-predict factors such as which zone was active when a particular callback was set.
It is important to use the same zone when calling ensureInitialized on the binding as when calling runApp later.

• 126798

This was reported #90 (comment) and #90 (comment).

Type of change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Maintenance
• New release

Related issues

This is being partially tracked here: #90, but the issue itself is about something else, so this wouldn't close the issue.

Checklists

Development

• Lint rules pass locally
• The code changed/added as part of this pull request has been covered with tests
• All tests related to the changed code pass in development

Code review

• This pull request has a descriptive title and information useful to a reviewer. There may be a screenshot or screencast attached
• "Ready for review" label attached to the PR and reviewers assigned
• Issue from task tracker has a link to this pull request
• Changes have been reviewed by at least one other engineer

[cyrusradfar]

thanks for the update @matux -- looks 🧱 solid