Add domain into the query for threat management

What does this MR do?

Add domain into the query for threat management related alerts. Default is nil so it will not impact alerts under monitoring. This MR ties the frontend with the backend.

Related backend code:

• https://gitlab.com/gitlab-org/gitlab/-/blob/master/ee/app/finders/ee/alert_management/alerts_finder.rb#L13
• https://gitlab.com/gitlab-org/gitlab/-/blob/master/app/graphql/types/alert_management/domain_filter_enum.rb#L10

Related issue: #287726 (closed)

Screenshots (strongly suggested)

Threat Monitoring

Alerts (under Operations)

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team