Enable scan execution policy builder on group level

What does this MR do and why?

Describe in detail what your merge request does and why.

This MR partially resolves #367278 (closed)

This MR enables feature flag for scan execution policy builder on a group level

User can build yaml configuration via UI controls.

When policy is created on group level it applies for all projects in a group.

Screenshots or screen recordings

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

Create policy
create_policy

check projects
merge

How to set up and validate locally

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

1. Make sure you have scan_execution_rule_mode feature flag enabled
2. Go to any group with projects
3. Go to Security & Compliance -> Policies
4. Create new policy
5. Make sure it is in policies list
6. Go to any project -> Security & Compliance -> Policies
7. Make sure policy was created for that project as well

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 #367278 (closed)