HCL2'ify the examples?

[wimax-grapl]

Hi there!
using packer hcl2_upgrade results in a few oddities, such as the following for nomad-consul[.pkr].json:

# 1 error occurred upgrading the following block:
# unhandled "clean_resource_name" call:
# there is no way to automatically upgrade the "clean_resource_name" call.
# Please manually upgrade to use custom validation rules, `replace(string, substring, replacement)` or `regex_replace(string, substring, replacement)`
# Visit https://packer.io/docs/templates/hcl_templates/variables#custom-validation-rules , https://www.packer.io/docs/templates/hcl_templates/functions/string/replace or https://www.packer.io/docs/templates/hcl_templates/functions/string/regex_replace for more infos.

This is easily solved, but - given that hcl2 is now recommended and default - why not upgrade the examples?

[brikis98]

We hit a number of issues with Packer/HCL when we tried it a while back. However, these have likely been fixed since. PR to update the examples is welcome!