infra(testing): upgrade AWS provider to 6.x

[inge4pres]

Motivation/summary

Upgrade the TF projects in testing and pin the AWS provider to latest 6.x release.

Related: found and fixed a bug in the EC2 module terraform-aws-modules/terraform-aws-ec2-instance#466

Checklist

How to test these changes

I was able to test both the benchmarks and smoke-test supported OS provisioning projects without issues.

Related issues

[github-actions]

🤖 GitHub comments

Just comment with:

• run docs-build : Re-trigger the docs validation. (use unformatted text in the comment!)

[mergify]

This pull request does not have a backport label. Could you fix it @inge4pres? 🙏
To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-7.17 is the label to automatically backport to the 7.17 branch.
• backport-8./d is the label to automatically backport to the 8./d branch. /d is the digit.
• backport-9./d is the label to automatically backport to the 9./d branch. /d is the digit.
• backport-active-all is the label that automatically backports to all active branches.
• backport-active-8 is the label that automatically backports to all active minor branches for the 8 major.
• backport-active-9 is the label that automatically backports to all active minor branches for the 9 major.

[elasticmachine]

💚 Build Succeeded

• Buildkite Build
• Commit: 0c708e1