Add option to switch to S3v2 driver for Container Registry storage

What does this MR do?

This change adds a new configuration option for AWS S3 storage drivers used by GitLab's container registry. It introduces a variable gitlab_object_storage_aws_driver that defaults to 's3' (AWS SDK v1) but can be set to 's3_v2' (AWS SDK v2). The change updates templates to use this variable instead of hardcoded 's3' values and adds documentation explaining that the older 's3' driver is planned for removal in GitLab 19.0, with AWS SDK v1 reaching end-of-life on July 31, 2025. This allows users to prepare for the upcoming deprecation by switching to the newer AWS SDK v2 driver when they're ready.

• https://docs.gitlab.com/update/deprecations/#s3-storage-driver-aws-sdk-v1-for-the-container-registry

Related issues

Closes Add option to switch to S3v2 driver for Contain... (#1051 - closed)

Author's checklist

When ready for review, the Author applies the workflowready for review label and mention @gitlab-org/software-delivery/get-maintainers:

• Merge request:
  • Corresponding Issue raised and reviewed by the GET maintainers team.
  • Merge Request Title and Description are up-to-date, accurate, and descriptive
  • MR targeting the appropriate branch
  • MR has a green pipeline
  • MR has no new security alerts in the widget from the Secret Detection and IaC Scan (SAST) jobs.
• Code:
  • Check the area changed works as expected. Consider testing it in different environment sizes (1k,3k,10k,etc.).
  • Documentation created/updated in the same MR.