Support Packer 1.8+

[sue445]

Fixes. #16

This contains following fixes.

• Upgrade to Packer 1.8.5
• Upgrade to Go 1.18
  • The current latest Go version is 1.20, but I have adapted it to the version of Go we use at Packer
  • c.f. https://github.com/hashicorp/packer/blob/v1.8.5/go.mod#L267
• Migrate to github.com/hashicorp/packer-plugin-sdk
  • Packer now recommends using github.com/hashicorp/packer-plugin-sdk
  • c.f. https://developer.hashicorp.com/packer/docs/plugins/creation
• Upgrade to latest modules
• Upgrade to Ruby 3.2 (for UAT)
• Update vendor/ (This is so big...)

This works on my repo (I'm using AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY for my AWS account)

• https://github.com/sue445/packer-provisioner-serverspec/pull/2
• https://app.circleci.com/pipelines/github/sue445/packer-provisioner-serverspec/14/workflows/b3bb8391-9443-43a0-a11d-4f3183bceaeb