Add "Prevent Force Pushing" setting

What does this MR do and why?

Add "Prevent Force Pushing" setting

• hide behind ":scan_result_policies_block_force_push" feature flag
• ensure feature flag is independent of both the ":scanResultPoliciesBlockUnprotectingBranches" and ":scanResultAnyMergeRequest" feature flags and works with them
• update tests

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

Scenario	Policy Editor Rule Mode	Yaml
scan_result_policies_block_force_push on
scanResultPoliciesBlockUnprotectingBranches on and scan_result_policies_block_force_push on
scanResultAnyMergeRequest on and scan_result_policies_block_force_push on
all on

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Enable a feature flag that adds settings

echo "Feature.enable(:scan_result_policies_block_force_push)" | rails c

2. Upload a GitLab Ultimate license
3. Navigate to a project/group => Secure => Policies => New policy => Scan Result Policy
4. Verify the setting displays and can be modified and reflected in the yaml correctly
5. Select a policy type
6. Verify the setting displays and can be modified and reflected in the yaml
7. Modify various feature flags and ensure they interact appropriately

echo "Feature.disable(:scan_result_policies_block_unprotecting_branches) && Feature.disable(:scan_result_any_merge_request)" | rails c

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 #428232 (closed)