[WIP - TEST] Migrate ecr pure sdk

[TheanLim]

Summary

Migrate ECR client to aws-sdk-go-v2.

Implementation details

• Migrate our v1 ECR client to v2 ECR SDK client
  • Migrate from the v1 bespoke ECR client to using the official ECR SDK.
  • Replace our v1 ECR types to v2 ECR types
  • Update GetAuthorizationToken() signature to match the v2 client's
    • Update GetAuthorizationTokenInput, which now takes in a slice of strings instead of an array of string pointers
  • Update ECR Client Construction per doc
    • Use aws-sdk-go-v2 config and credentials instead of v1 aws.NewConfig(), credentials and session. Configuration Loading doc for reference
    • Get instancecreds referring to #4446
    • Replace cfg.BaseEndpoint with cfg.Endpoint
    • Replace aws.StringValue -> aws.ToString, aws.TimeValue -> aws.ToTime, aws.IntValue -> aws.ToInt
• Generate ECR mocks (for v2 client)
• Remove our v1 ECR Client
• Update vendor modules for the agent module.

Testing

Github checks pass.

New tests cover the changes: no

Description for the changelog

Migrate ECR client to aws-sdk-go-v2.

Licensing

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.