Persist approval_settings and any_merge_request rules in policies

What does this MR do and why?

This MR introduces changes so that we start persisting approval_settings and any merge request rules from policies in scan_result_policies table.

Screenshots or screen recordings

scan_result_policies record:

approval_project_rules record for any_merge_request rule:

How to set up and validate locally

1. Go to Secure -> Policies
2. Create new Scan Result Policy
3. Switch to the .yaml mode and use the following YAML:

   type: scan_result_policy
   name: Any unsigned MR
   description: ''
   enabled: true
   rules:
     - type: any_merge_request
       branch_type: protected
       commits: unsigned
   actions:
     - type: require_approval
       approvals_required: 1
       user_approvers_ids:
         - 4 # Change to any existing user ID with access to the project
   approval_settings:
     prevent_approval_by_author: true
     prevent_approval_by_commit_author: false
     remove_approvals_with_new_commit: false
     require_password_to_approve: true

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #418752 (closed)