Update packer version used in pipelines

What does this MR do?

Update packer in build pipeline containers to the latest available version.

Related issues

Related #6504 (closed)

Test plan

• Check build logs to ensure BUILDER_IMAGE_REVISION=3.8.0
• Build and deploy AMI image locally using released debian_packer:3.8.0 container. Test for basic operation.

Checklist

See Definition of done.

For anything in this list which will not be completed, please provide a reason in the MR discussion

Required

• Merge Request Title, and Description are up to date, accurate, and descriptive
• MR targeting the appropriate branch
• MR has a green pipeline on GitLab.com
• Pipeline is green on the dev.gitlab.org mirror for this branch if the change is touching anything besides documentation or internal cookbooks. Please note that feature branches are not automatically mirrored to dev.gitlab.org, and should be manually pushed whenever necessary.
• trigger-package has a green pipeline running against latest commit

Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes
• Documentation created/updated
• Tests added
• Integration tests added to GitLab QA
• Equivalent MR/issue for the GitLab Chart opened
• Validate potential values for new configuration settings. Formats such as integer 10, duration 10s, URI scheme://user:passwd@host:port may require quotation or other special handling when rendered in a template and written to a configuration file.