Fix updateConfig to overwrite monitor epic config options

[ravjotbrar]

Currently, the updateConfig endpoint appends monitoring settings to the config instead of overwriting them:

  valkey: {},
  server: {
    port: 0,
    data_dir: '/Users/Ravjot.Brar/Library/Application Support/Valkey Admin/metrics-data/localhost-6380'
  },
  collector: { batch_ms: 60000, batch_max: 500 },
  epics: [
    {
      name: 'memory',
      type: 'memory_stats',
      poll_ms: 5000,
      file_prefix: 'memory'
    },
    {
      name: 'cpu',
      type: 'info_cpu',
      poll_ms: 5000,
      file_prefix: 'cpu'
    },
    {
      name: 'commandlog_large_reply',
      type: 'commandlog_large_reply',
      poll_ms: 10000,
      file_prefix: 'commandlog_large_reply'
    },
    {
      name: 'commandlog_large_request',
      type: 'commandlog_large_request',
      poll_ms: 10000,
      file_prefix: 'commandlog_large_request'
    },
    {
      name: 'commandlog_slow',
      type: 'commandlog_slow',
      poll_ms: 10000,
      file_prefix: 'commandlog_slow'
    },
    {
      name: 'slowlog_len',
      type: 'slowlog_len',
      poll_ms: 60000,
      file_prefix: 'slowlog_len'
    },
    {
      name: 'monitor',
      type: 'monitor',
      monitoringDuration: 10000,
      monitoringInterval: 10000,
      maxCommandsPerRun: 1000000,
      file_prefix: 'monitor'
    }
  ],
  monitoring: { monitorEnabled: true, monitorDuration: 1000 }
}

The expected result overwrites monitoringDuration and uses monitorEnabled in the metrics server instead of the frontend (this is related to refactoring ownership of config options like lfuEnabled to the metrics server).