Security Policy Drawer handles cluster image scanning policies

What does this MR do and why?

Describe in detail what your merge request does and why.

This MR resolves #346188 (closed)

This MR adds option for agents to display human-readable rules in policy drawer

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before

after

How to set up and validate locally

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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(:scan_execution_rule_mode)

2. Go to URL/root/PROJECT_ID/-/security/policies
3. Create new policy for scan execution with schedule rule
4. Return to policy list
5. Open side drawer by selecting scan execution policy
6. You should see rule in list with parsed cadence

MR acceptance checklist

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

Related to #346188 (closed)