Previously the test harness was preloading schemas from the providers
before running any test steps.
Since terraform.NewContext already deals with loading provider schemas,
we can instead just use the schemas it loaded for our shimming needs,
avoiding the need to reimplement the schema lookup behavior and thus
the need to create a throwaway provider instance with which to do it.
This folder contains helper libraries for Terraform plugins. A running
joke is that this is "Terraform standard library" for plugins. The goal
of the packages in this directory are to provide high-level helpers to
make it easier to implement the various aspects of writing a plugin for
Terraform.
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