AV-272399 fix(pool): suppress ip.addr requirement when resolve_server_by_dns is enabled

[Rohan-sss1]

1. Creating a pool using the Terraform pool resource, and the controller will resolve the IP.
2. The Terraform plan will call the GET API; at that time, the diffsuppress function will replace the new IP with the old (user-provided IP) so it will not show a diff.
3. This will only suppress the diff if resolve_server_by_dns is set to true.

Test status

Scenarios handled and tested correctly

Scenario	Before	After
hostname → 1 IP resolved	✓ no diff	✓ no diff
hostname → 2+ IPs resolved	diff (extra servers shown as deleted)	✓ no diff (all resolved entries kept)
hostname not yet resolved (all 0.0.0.0)	✓ placeholder kept	✓ placeholder kept
first apply (empty old state)	✓ placeholder sent	✓ placeholder sent
user removes hostname server	✓ diff shown	✓ diff shown
user provides explicit IP	✓ diff shown normally	✓ diff shown normally