Add beta channel to static analysis tests so that we get early warning of failures.

[cpswan]

Which at_widget package you want to add enhancement?

at_backupkey_flutter, at_chat_flutter, at_common_flutter, at_contacts_flutter, at_contacts_group_flutter, at_events_flutter, at_follows_flutter, at_invitation_flutter, at_location_flutter, at_login_flutter, at_notify_flutter, at_onboarding_flutter, at_sync_ui_flutter, at_theme_flutter

On what platforms do you want to add enhancement?

Linux

Is your feature request related to a problem?

#842 and #843 illustrate that we shouldn't wait for tests to fail against stable releases.

Describe the solution that you'd like

Run static analysis against beta channel (as well as stable)

Describe alternatives that you have considered

No response

Additional context

We will need to redefine mandatory tests.