FE: Update security policies drawer for scan execution policy with agents/namespaces

Why are we doing this work

• for scan execution policies with branches, the Summary of the policy drawer lists out all the branches in a readable way
• for scan execution policies with agents or namespaces (as defined in the docs: Add agents to Scan Execution Policies documenta... (!96148 - merged)), the agents and namespaces are not listed out in a human-readable way in the policy drawer
• users want to see their scan execution policy yaml containing agents and namespaces in a more readable way

Relevant links

Sample Yaml

type: scan_execution_policy
name: Enforce CIS
description: This policy is great!
enabled: true
rules:
  - type: schedule
    cadence: 0 * * * *
    agents:
      cis-agent:
        namespaces:
          - production
  - type: schedule
    agents:
      staging-agent:
        namespaces:
          - staging
    cadence: 0 * * * *
actions:
  - scan: container_scanning
  - scan: sast

Type	Policy	Policy Drawer	Current summary	Suggested summary
Policy with agents				Scans to be performed by the cis-agent for the production namespace every hour, every day. Scans to be performed by the staging-agent agent for the staging namespace every hour, every day.

Related to #346188 (closed)

Implementation plan

• frontend update policy_drawer/scan_execution_policy.vue to show the agents and namespaces
  • Scans to be performed by the XXX agent for all namespaces every hour, every day.
  • Scans to be performed by the XXX agent for the XXX namespaces every hour, every day.

Verification steps

1. Navigate to a project => Security & Compliance => Policies => New policy => Scan execution policy => yaml mode
2. Enter in the above yaml and merge the MR
3. Navigate to the project => Security & Compliance => Policies => Select the new policy
4. View the drawer