feat: Implement API to set NTP servers

[hanyux-nv]

Added a new Redfish API method set_ntp_servers that configures a list of NTP servers of the BMC.

See issue #548.

[spydaNVIDIA]

lgtm!

[krish-nvidia]

For Dells, you have to issue the following redfish call. Out of experience, setting them in NetworkProtocols doesn't work 😅

curl -sku "username:password" \
  -X PATCH \
  -H "Content-Type: application/json" \
  -d '{
    "Attributes": {
      "NTPConfigGroup.1.NTPEnable": "Enabled",
      "NTPConfigGroup.1.NTP1": "pool.ntp.org",
      "NTPConfigGroup.1.NTP2": "time.google.com"
    }
  }' \
  "https://<iDRAC_IP>/redfish/v1/Managers/iDRAC.Embedded.1/Attributes"

[krish-nvidia]

See comment above ^

[krish-nvidia]

For HPEs, you have to use /redfish/v1/Managers/1/DateTime to set the NTP servers. Other vendors might require other paths as well so I'd try them out on each machine to make sure it works.