Update policies#new view to pass up updated data

What does this MR do?

As part of &5362 (closed), we are moving the Policies list/actions from threat_monitoring_controller to policies_controller AND adding a new type of policy. Thus, we were reusing the policies_details helper method, but now that the new policy type is in the code and there are new paths, the helper (which we were going to move over to policies_helper in the cleanup) needs to be copied and modified.

I have updated the feature flag cleanup issue to reflect the cleanup of removing policies_details and renaming threat_monitoring_path

Update policies#new view to pass up new data

• update helper to account for a new policy as well as editing a policy

Screenshots or Screencasts (strongly suggested)

No visual changes as the only other page that is set up to use this data has no frontend yet

This entire feature is behind a feature flag

Does this MR meet the acceptance criteria?

Conformity

• I have included changelog trailers, or none are needed. (Does this MR need a changelog?)
• I have added/updated documentation, or it's not needed. (Is documentation required?)
• I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• I have added information for database reviewers in the MR description, or it's not needed. (Does this MR have database related changes?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.
• This change is backwards compatible across updates, or this does not apply.

Availability and Testing

• I have added/updated tests following the Testing Guide, or it's not needed. (Consider all test levels. See the Test Planning Process.)
• I have tested this MR in all supported browsers, or it's not needed.
• I have informed the Infrastructure department of a default or new setting change per definition of done, or it's not needed.

Security

Does this MR contain changes to processing or storing of credentials or tokens, authorization and authentication methods or other items described in the security review guidelines? If not, then delete this Security section.

• 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 #321884 (closed)