As a HyperShift operator
I want STS migrated to AWS SDK v2 with foundation infrastructure
So that AWS authentication works with the new SDK

Acceptance Criteria:

• [ ] Add AWS SDK v2 dependencies to go.mod
• [ ] Create custom interface layer in /support/awsutil/interfaces.go
• [ ] Implement v2 configuration utilities in /cmd/infra/aws/util/
• [ ] Migrate STS authentication code
• [ ] All authentication flows work (assume role, cross-account, OIDC)
• [ ] Unit and E2E tests pass

Files:

• /support/awsutil/interfaces.go (new)
• /cmd/infra/aws/util/config_v2.go (new)
• /cmd/infra/aws/util/sts.go
• /cmd/infra/aws/create_cli_role.go