* terraform: improve provider config related error messages with nil
config
If there is no provider configuration present in the config at all,
errors related to missing required arguments lack source information or
even a reference to the provider in question. This PR adds more specific
error messages in three of these situations:
- ValidateProvider
- ConfigureProvider: provider.PrepareProviderConfig
- ConfigureProvider: ctx.ConfigureProvider
To test the last case I added a ConfigureProviderFn to the MockContext.
* remove newlines and let the diagnost renderer handle fit
Before configuring a provider, we need to unmark the configuration
object, in case it includes any sensitive values. This is required
because configuration occurs over gRPC, which doesn't support sensitive
marks.
* remove leftover debug line
* terraform: refactor ProviderEvalTree
This PR refactors the ProviderEvalTree by folding the entire tree into
straight-through code in NodeApplyableProvider Execute (formally
EvalTree). The EvalConfigProvider functions were refactored into
NodeApplyableProvider functions (since that was the only place they were
used).
I also removed the unused node_provider_disabled code.
* revert removal of graphNodeCloseProvider EvalTree, replace with Execute
