[Imprv] add functionality to update subnets to module ntnx_subnets

[bhati-pradeep]

Describe the request
Add functionality to update subnets in ntnx_subnets. Identify such subnet components which can be updated and add functionality as per that.

Current behaviour
It only allows creation and delete

Expected behaviour
Should be able to update subnet

Refer docs: https://www.nutanix.dev/api_references/prism-central-v3/#/c4c4a9a81a449-update-a-existing-subnet

[OpsCharlie]

I have the same issue.
When using name it creates a duplicate subnet

- name: VLAN subnet with IPAM, IP pools and DHCP
  nutanix.ncp.ntnx_subnets:
    name: "{{ ntnx_subnet.name }}"
    state: present
    vlan_subnet:
      vlan_id: "{{ ntnx_subnet.vlan_id }}"
      ....

When using subnet_uuid to "update" the subnet, it is mutual excluded:

- name: VLAN subnet with IPAM, IP pools and DHCP
  nutanix.ncp.ntnx_subnets:
    subnet_uuid "{{ ntnx_subnet.name }}"
    vlan_subnet:
      vlan_id: "{{ ntnx_subnet.vlan_id }}"
      ....

fatal: [localhost]: FAILED! => {"changed": false, "msg": "parameters are mutually exclusive: vlan_subnet|external_subnet|subnet_uuid|overlay_subnet"}

[bhati-pradeep]

@OpsCharlie It is expected as subnet update is not yet supported. So for state="present" it will aways try to create a new subnet.

[gdmjoho]

#424