fix(GetUnusedAll) - JSON concatenation

[doronkg]

This PR aims to resolve #226.
Currently when executing GetUnusedAll() with JSON format, instead of merging the two lists, it appends them.
This also resolves the Error parsing JSON: invalid character '{' after top-level value returned from kor exporter.

Before the fix:

$ kor all -o json
{
  "test": {
    "ConfigMap": null,
    "DaemonSet": null,
    "Deployment": null,
    "Hpa": [
      "php-apache"
    ],
    "Ingress": [
      "test-ingress-1-work"
    ],
    "Job": null,
    "Pdb": null,
    "Pvc": [
      "myclaim"
    ],
    "ReplicaSet": null,
    "Role": null,
    "Secret": null,
    "Service": [
      "app1-service",
      "app2-service"
    ],
    "ServiceAccount": null,
    "StatefulSet": null
  }
}{
  "": {
    "ClusterRole": [
      "admin",
      "view"
    ],
    "Crd": [
      "thanosrulers.monitoring.coreos.com"
    ],
    "Pv": null,
    "StorageClass": null
  }
}

After the fix:

$ kor all -o json
{
  "": {
    "ClusterRole": [
      "admin",
      "view"
    ],
    "Crd": [
      "thanosrulers.monitoring.coreos.com"
    ],
    "Pv": null,
    "StorageClass": null
  },
  "test": {
    "ConfigMap": null,
    "DaemonSet": null,
    "Deployment": null,
    "Hpa": [
      "php-apache"
    ],
    "Ingress": [
      "test-ingress-1-work"
    ],
    "Job": null,
    "Pdb": null,
    "Pvc": [
      "myclaim"
    ],
    "ReplicaSet": null,
    "Role": null,
    "Secret": null,
    "Service": [
      "app1-service",
      "app2-service"
    ],
    "ServiceAccount": null,
    "StatefulSet": null
  }
}

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 25 lines in your changes are missing coverage. Please review.

Project coverage is 47.20%. Comparing base (4a79f02) to head (6cda98e).

Files	Patch %	Lines
pkg/kor/all.go	0.00%	25 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##             main     #227      +/-   ##
==========================================
- Coverage   47.58%   47.20%   -0.38%     
==========================================
  Files          32       32              
  Lines        2915     2938      +23     
==========================================
  Hits         1387     1387              
- Misses       1354     1377      +23     
  Partials      174      174              

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[yonahd]

LGTM. Thanks!