Add policy alert picker

What does this MR do?

Add policy alert picker

• hide it behind threatMonitoringAlerts feature flag
• update to_yaml file to handle annotations
• create alert-picker component to allow for picker creation
• on alert addition, update yaml file to include corret url and status

How to reproduce

NOTE: this is behind a feature flag

1. Follow this video on creating a fake cluster/env locally
2. Enable the feature flag (cd path/to/gitlab && rails c && Feature.enable(:threat_monitoring_alerts))
3. Navigate to Security & Compliance -> Threat Monitoring -> Policy tab
4. Add a new alert
5. Test out the cool new feature! And open up your browser developer tools to view the request made when clicking the Add policy button (Note: Testing the full thing WITH a kubernetes cluster is currently not possible as the backend is still in progress, but ⏲ )

Screenshots (strongly suggested)

Page	Before	After
with feature flag	-
w/out feature flag	-
New Rule button

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

Related to #238484 (closed)