FE: Allow for alert dismissal

Why are we doing this work

• when a user has remedied an alert, they want to dismiss it so that they know no more actions are required
• allow a user to dismiss the alert

Design

• https://www.youtube.com/watch?v=HuZgaMKdJF0&feature=youtu.be

Non-functional requirements

• Documentation: I am waiting until the end to update the documentation as this feature is behind a feature flag
• Feature flag: This feature is behind the threat_monitoring_alerts feature flag
• Testing

Implementation plan

• frontend copy the get mutation from https://gitlab.com/gitlab-org/gitlab/-/blob/master/app/assets/javascripts/alert_management/graphql/mutations/update_alert_status.mutation.graphql or reuse it to set the status of an alert to dismiss/ignored (as seen here)
• frontend add a column to the table that has a button that allows for a user to dismiss the alert
  • when an alert is dismissed, the button should read undo dismissal
  • create a dropdown that allows for status change