Auth Provider Cmd Duplicate Call

--auth-provider-cmd no longer runs once per dependency cache directory

Resolving dependency outputs ran the configured --auth-provider-cmd again from inside each .terragrunt-cache working directory, on top of the call already made for the unit.

Terragrunt now reuses the credentials already obtained for the dependency when reading outputs from a cached working directory, so --auth-provider-cmd is invoked once per dependency instead of twice.