Konnect Platform: AWS Private link API and Terraform instructions

## Definition of done
- Add API, UI, and Terraform tabs to https://developer.konghq.com/gateway-manager/aws-private-link/ with instructions about how to configure them
- API steps: https://docs.google.com/document/d/1JZQAU5Sde3yc5LKTXYFwpGNCeUUhOlYjljKmqNn6FSA/edit?tab=t.0
- Terraform: will need info on these

## Information
Slack: https://kongstrong.slack.com/archives/CDSTDSG9J/p1758516134282689
DRP: Smriti

## Due date (optional)

n/a

## Size
Large

Start by locating the source for the Gateway Manager AWS Private Link page at developer.konghq.com and read the linked Google document for the API steps. Confirm the missing Terraform details through the referenced Slack thread, then add API, UI, and Terraform tabs with configuration instructions; done means all three tabs are present and cover the requested setup.

Written by the indexing model from the issue text.