Ambiguous Unit Stack Errors

Ambiguous unit/stack components now throw errors

Previously, Terragrunt would silently engage in undefined behavior when both a terragrunt.hcl and terragrunt.stack.hcl file existed in the same directory.

With this release, Terragrunt will start to throw warnings and prevent such usage. Users will have to ensure that only one of a unit (terragrunt.hcl) or stack configuration (terragrunt.stack.hcl) exist in a unit or stack directory, respectively.