Fix L7 policies not being saved properly

What does this MR do?

Fix L7 policies not being saved properly

• if the UI does not support L7 policies currently
• if the user is in yaml mode, save the yaml file

Screenshots (strongly suggested)

Before	After

After

➜  gitlab git:(271169-fix-l7-policies) kubectl exec -it -n gitlab-managed-apps -c cilium-agent cilium-xvzn2 -- /bin/bash
root@minikube:/home/cilium# cilium policy get
[
  ...,
  {
    "endpointSelector": {
      "matchLabels": {
        "k8s:io.kubernetes.pod.namespace": "network-policy-demo-cluster-management-5000174-production"
      }
    },
    "ingress": [
      {
        "toPorts": [
          {
            "ports": [
              {
                "port": "80",
                "protocol": "TCP"
              },
              {
                "port": "443",
                "protocol": "TCP"
              }
            ],
            "rules": {
              "http": [
                {
                  "headers": [
                    "X-Forwarded-For: 192.168.1.1"
                  ]
                }
              ]
            }
          }
        ],
        "fromEntities": [
          "cluster"
        ]
      }
    ],
    "labels": [
      {
        "key": "io.cilium.k8s.policy.derived-from",
        "value": "CiliumNetworkPolicy",
        "source": "k8s"
      },
      {
        "key": "io.cilium.k8s.policy.name",
        "value": "limit-inbound-ip-02",
        "source": "k8s"
      },
      {
        "key": "io.cilium.k8s.policy.namespace",
        "value": "network-policy-demo-cluster-management-5000174-production",
        "source": "k8s"
      },
      {
        "key": "io.cilium.k8s.policy.uid",
        "value": "a4b46ef8-57cb-43a6-8720-d7adc7342077",
        "source": "k8s"
      }
    ]
  },
  ...
]

How to test

https://gitlab.com/-/snippets/2070592

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team

Related to #271169 (closed)