Relying on the early config for provider requirements was necessary in
Terraform 0.12, to allow the 0.12upgrade command to run after init
installs providers.
However in 0.13, the same restrictions do not apply, and the detection
of provider requirements has changed. As a result, the early config
loader gives incorrect provider requirements in some circumstances,
such as those in the new test in this commit.
Therefore we are changing the init command to use the requirements found
by the full configuration loader. This also means that we can remove the
internal initwd CheckCoreVersionRequirements function.
62d826e066