Merge terraform-google-conversion and terraform-validator repositories

[melinath]

Currently, we have separate terraform-google-conversion and terraform-validator repositories. This is for historical reasons that no longer apply. We would like to combine them so that it is easier for contributors to add support for additional resources; the split is a constant source of confusion. This will also simplify making sure that changes made in Magic Modules don't break terraform-validator; currently, it's easy to make a version of terraform-google-conversion that passes its tests but doesn't work with terraform-validator.

This work should accomplish the following:

• Rename mmv1/provider/terraform_object_library.rb to terraform_validator.rb PR
• Update build process to refer to validator instead of google-conversion
• Update build process to generate the code into a subdirectory of terraform-validator and run terraform-validator tests (including integration tests) TFV PR MM PR
• Add a note to terraform-google-conversion to state that it is deprecated. (We can't delete it, at least for now, because older terraform-validator versions depend on it.)
• Update make commands & documentation to reflect the new build process PR
• Update issue templates to not reference terraform google conversion PR

[morgante]

Love this idea. 👍 There was a time when we thought -conversion might be generally useful, but it seems clear that a separate repo isn't required.

[melinath]

This part of the process is complete. The follow-up work re: running resource tests upstream is covered by #332

[marktru]

Internal issue: b/211890077

[melinath]

This has been resolved