* Refactor provider validation into separate func & recurse
Refactors the validate provider functions into a separate function
that can recursively search above a module to check and see if
any parents of the module contain count/for_each configs to be
considered
Validate providers in expanding modules. Expanding modules cannot have provider configurations with non-empty configs, which includes having a version configured. If an empty or alias-only block is passed, the provider must be passed through the providers argument on the module call
Previously, adding a version constraint to a module that was previously
recorded without a version in the module manifest would cause a panic.
Instead, we now use a slight variant of the "dependencies have changed"
error that doesn't try to print out a specific version number.
Previously the behavior for loading and installing modules was included in
the same package as the representation of the module tree (in the
config/module package).
In our new world, the model of a module tree (now called a "Config") is
included in "configs" along with the Module and File structs. This new
package replaces the loading and installation functionality previously
in config/module with new equivalents that work with the model objects
in "configs".
As of this commit, only the loading functionality is implemented. The
installation functionality will follow in subsequent commits.