Report & add missing module versions

[radeksimko]

Context

Some users may end up producing configuration such as the following example:

module "name" {
  source = "terraform-aws-modules/eks/aws"
}

^ i.e. without explicitly defining which version(s) of the module do they want/expect

This represents poor practice because it ignores the fact that modules may (and often do) introduce breaking changes.

Proposal

• Report missing version for Registry modules as a warning diagnostic
• Provide a quickfix code action which adds the version constraint based on latest available major version, such as version = "~> 19.17" for terraform-aws-modules/eks/aws