terragrunt validate - issues with root terragrunt.hcl

Failures in root terragrunt.hcl terragrunt validate.
Consider the following dir structure

```
├── dev
│   └── eu-west-1
│   └── project
│   └── terragrunt.hcl
└── terragrunt.hcl
└── common.hcl
```

Where the child includes the parent via `find_in_parent_folders()`.

If the parent has many `read_terraform_config(find_in_parent_folders("common.hcl"))` type includes it will fail when terragrunt validate runs against it in singular. As the dir traversal fails to find the file.

Anything that can be done about this?

Start by reproducing terragrunt validate with the shown dev/eu-west-1/project/terragrunt.hcl layout, the root terragrunt.hcl, and common.hcl. Check how find_in_parent_folders() and read_terraform_config() resolve paths when validation runs on the root file. Done means validation handles these parent references without failing during directory traversal.

Scritto dal modello di indicizzazione a partire dal testo della issue.