Add policy scope section for security policies

What does this MR do and why?

This initial MR for #428494 (closed)

Scope of this MR is to add new section for Policy scope for scan result policy and scan execution policy.

Policy scope components is not finished in this MR (behind feature flag).

This issue is broken down into multiple MR's for better review.

Screenshots or screen recordings

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

UI	Description	Scope
	Scan result policy	Group
	Scan execution policy	Group
	Scan execution policy	Project

How to set up and validate locally

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

1. Enable Feature Flag

   Feature.enable(:security_policies_policy_scope)  

2. Go to a Group -> Secure -> Policies -> New policy -> New scan result/execution policy -> check Policy scope section is there.

3. Go to Project -> Secure -> Policies -> New policy -> New scan result/execution policy -> check Policy scope section is not there.

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 #428494 (closed)