Support display_name argument in network_link_service data source

[t0ffel]

Release Notes

New Features

• Add display_name argument to network_link_service data source. Make id argument optional

Bug Fixes

• [Briefly describe any bugs fixed in this PR].

Examples

• [Briefly describe any Terraform configuration example updates in this PR].

Checklist

• I can successfully build and use a custom Terraform provider binary for Confluent.
• I have verified my PR with real Confluent Cloud resources in a pre-prod or production environment, or both.
• I have attached manual Terraform verification results or screenshots in the Test & Review section below.
• I have included appropriate Terraform acceptance or unit tests for any new resource, data source, or functionality.
• I confirm that this PR introduces no breaking changes or backward compatibility issues.
• I have updated the corresponding documentation and include relevant examples for this PR.
• I have indicated the potential customer impact if something goes wrong in the Blast Radius section below.
• I have put checkmarks below confirming that the feature associated with this PR is enabled in:
  • Confluent Cloud prod
  • Confluent Cloud stag
  • Check this box if the feature is enabled for certain organizations only

What

Addresses #548
Usually when using data source we want to get the id of the resource given some parameters like display name. The PR allows for exactly that.

Blast Radius

data source is read-only, won't apply any changes.

References

#548

Test & Review

tested with acceptance tests and used the provider manually to obtain NLS data source.