Add new unauthenticated route for reporting stats API

[abbashus]

Issue #, if available:

Description of changes:
This change introduces new unauthenticated route for Kibana reporting stats API api/reporting/stats.
The API exposes operational and business metrics for Kibana Reporting plugin.
See opendistro-for-elasticsearch/kibana-reports#277

Sample response:

  {
  "report": {  
    "create": {  # POST /api/reporting/generateReport
      "count": 0,
      "system_error": 0,
      "user_error": 3,
      "total": 0
    },
    "create_from_definition": {  # POST /api/reporting/gemerateReport/{reportDefinitionId}
      "count": 1,
      "system_error": 0,
      "user_error": 0,
      "total": 1
    },
    "download": {  # GET /api/reporting/generateReport/{reportId}
      "count": 5,
      "system_error": 0,
      "user_error": 0,
      "total": 5
    },
    "list": {  # GET /api/reporting/reports
      "count": 7,
      "system_error": 0,
      "user_error": 0,
      "total": 7
    },
    "info": {  # GET /api/reporting/reports/{reportId}
      "count": 1,
      "system_error": 0,
      "user_error": 0,
      "total": 1
    }
  },
  "report_definition": {
    "create": {  # POST /api/reporting/reportDefinition
      "count": 0,
      "system_error": 0,
      "user_error": 0,
      "total": 0
    },
    "list": {  # GET /api/reporting/reportDefinitions
      "count": 7,
      "system_error": 0,
      "user_error": 0,
      "total": 7
    },
    "info": {  # GET /api/reporting/reportDefinition/{reportDefinitionId}
      "count": 3,
      "system_error": 0,
      "user_error": 0,
      "total": 3
    },
    "update": {   # PUT /api/reporting/reportDefinition/{reportDefinitionId}
      "count": 0,
      "system_error": 0,
      "user_error": 0,
      "total": 0
    },
    "delete": {   # DELETE /api/reporting/reportDefinition/{reportDefinitionId}
      "count": 1,
      "system_error": 0,
      "user_error": 0,
      "total": 1
    }
  },
  "report_source": {   # GET /api/reporting/reportSource/{reportSourceType}
    "list": {
      "count": 3,
      "system_error": 0,
      "user_error": 0,
      "total": 3
    }
  },
  "dashboard": {
    "pdf": {
      "download": {
        "count": 1,
        "total": 1
      }
    },
    "png": {
      "download": {
        "count": 1,
        "total": 1
      }
    }
  },
  "visualization": {
    "pdf": {
      "download": {
        "count": 0,
        "total": 0
      }
    },
    "png": {
      "download": {
        "count": 0,
        "total": 0
      }
    }
  },
  "saved_search": {
    "csv": {
      "download": {
        "count": 4,
        "total": 4
      }
    }
  }
}

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[yuxitang-amzn]

Please fix the lint error.

[codecov]

Codecov Report

Merging #697 (c2fa2d6) into main (6d455e7) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #697   +/-   ##
=======================================
  Coverage   74.59%   74.59%           
=======================================
  Files          85       85           
  Lines        1842     1842           
  Branches      237      237           
=======================================
  Hits         1374     1374           
  Misses        413      413           
  Partials       55       55           

Impacted Files	Coverage Δ
...o_security/public/apps/configuration/constants.tsx	85.71% <0.00%> (ø)

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[abbashus]

Fixed the lint error.