Add PATCH Request Scenario to kperf for Evaluating Latency of Mutating API Calls

[vittoriasalim]

This PR introduces a new scenario in kperf to benchmark the latency of PATCH operations on Kubernetes resources. It focuses on measuring the performance impact of partial updates during the resource lifecycle, simulating realistic mutation patterns such as updating metadata and container specs.

Patch API Request

PATCH https://{api-server}/api/v1/namespaces/kperf/pods/test-pod4?timeout=1m0s 200 OK in 589 milliseconds

Patch Use Case

JSON Patch

- patch:
    version: v1
    resource: pods
    namespace: kperf
    patchType: json
    name: test-pod4
    body: |
      [
        {
          "op": "replace",
          "path": "/metadata/labels",
          "value": {}
        }
      ]
  shares: 100

• Operation: Replaces all labels with an empty map using RFC 6902 JSON Patch.
• Use Case: Precise, low-overhead field modification; ideal for fine-grained updates.

---

Merge Patch

- patch:
    version: v1
    resource: pods
    namespace: kperf
    patchType: merge
    name: test-pod4
    body: |
      {
        "metadata": {
          "labels": {
            "test-label": "mutation-test"
          }
        }
      }
  shares: 100

• Operation: Adds or replaces the metadata.labels field.
• Use Case: Simple map updates (e.g., labels or annotations); fast and widely supported.

---

Strategic-Merge Patch

- patch:
    version: v1
    resource: pods
    namespace: kperf
    patchType: strategic-merge
    name: test-pod4
    body: |
      {
        "spec": {
          "containers": [
            {
              "name": "fake-container",
              "image": "busybox:1.36"
            }
          ]
        }
      }
  shares: 100

• Operation: Updates the container image by identifying the container via its name using Kubernetes' strategic merge strategy.
• Use Case: Schema-aware patching for built-in resources; safely updates fields inside structured arrays like containers.

[vittoriasalim]

Addressed #187 (comment) #187 (comment)

Move validation to Request Patch Validate()
Error handling for incorrect patch types. If an invalid patch type is provided, the system will throw following error:

kperf: idx: 0 request: unknown patch type: strategic-mergd (valid types: json, merge, strategic-merge)

[fuweid]

Suggestion adding function instead of exported var.

func GetCliJSONPatchType(name string) (string, bool) {
        switch name {
        case "json":
             return "application/json-patch+json", false
        ...
}

You can handle it in the following-up.