bin: add support for full config JSON schema (-J)

[edsiper]

The following patch introduces an extension to the config helper by providing a full JSON schema. It can be triggered as follows:

fluent-bit -J

This is the pretty printed version of the JSON output:

{
  "fluent-bit": {
    "version": "1.9.0",
    "schema_version": "1",
    "os": "linux"
  },
  "customs": [
    {
      "type": "custom",
      "name": "calyptia",
      "description": "Calyptia Cloud",
      "properties": {
        "options": [
          {
            "name": "api_key",
            "description": "Calyptia Cloud API Key.",
            "default": null,
            "type": "string"
          },
          {
            "name": "store_path",
            "description": "",
            "default": null,
            "type": "string"
          },
          {
            "name": "calyptia_host",
            "description": "",
            "default": null,
            "type": "string"
          },
          {
            "name": "calyptia_port",
            "description": "",
            "default": null,
            "type": "string"
          },
          {
            "name": "calyptia_tls",
            "description": "",
            "default": "true",
            "type": "boolean"
          },
          {
            "name": "calyptia_tls.verify",
            "description": "",
            "default": "true",
            "type": "boolean"
          },
          {
            "name": "add_label",
            "description": "Label to append to the generated metric.",
            "default": null,
            "type": "space delimited strings (minimum 1)"
          },
          {
            "name": "machine_id",
            "description": "Custom machine_id to be used when registering agent",
            "default": null,
            "type": "string"
          }
        ]
      }
    }
  ],
  "inputs": [
    {
      "type": "input",
      "name": "cpu",
      "description": "CPU Usage",
      "properties": {
        "options": [
          {
            "name": "pid",
            "description": "Configure a single process to measure usage via their PID",
            "default": "-1",
            "type": "integer"
          },
          {
            "name": "interval_sec",
            "description": "Set the collector interval",
            "default": "1",
            "type": "integer"
          },
          {
            "name": "interval_nsec",
            "description": "Set the collector interval (sub seconds)",
            "default": "0",
            "type": "integer"
          }
        ]
      }
    },
    ......(redacted).......
            }
        ]
      }
    }
  ]
}

attached is tarball with the full content: 1.9.0.schema.json.tar.gz

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Fluent Bit is licensed under Apache 2.0, by submitting this pull request I understand that this code will be released under the terms of that license.