Use the configured providers directly, rather than looking for inherited
provider configuration during graph evaluation.
First remove the provider config cache, and the associated
SetProviderConfig and ParentProviderConfig methods on the eval context.
Every provider must be configured, so there's no need to look for
configuration from other provider instances.
The config.ProviderConfig struct now has a Scope field which stores the
proper path for the interpolation scope. To get this metadata to the
interpolator, we add an EvalInterpolatProvider node which can carry the
ProviderConfig, and an InterpolateProvider context method to carry the
ProviderConfig.Scope into the InterplationScope.
Some of the tests could be adjusted to account for the new inheritance
behavior, and some were simply no longer valid and will be removed.
The remaining tests have questions on how they should work in practice.
This mostly concerns orphaned modules where there is no longer a way to
obtain a provider. In some cases we may require that a minimal provider
config be present to handle the destroy process, but we need further
testing.
All disabled code was commented out in this commit to record any
additional comments. The following commit will be a cleanup pass.
Remove the Input flag threaded through the input graph creation process
to prevent interpolation failures on module variables.
Use an EvalOpFilter instead to inset the correct EvalNode during
walkInput. Remove the EvalTryInterpolate type, and use the same
ContinueOnErr flag as the output node for consistency and to try and
keep the number possible eval node types down.
Allow module variables to fail interpolation during input. This is OK
since they will be verified again during Plan. Because Input happens
before Refresh, module variable interpolation can fail when referencing
values that aren't yet in the state, but are expected after Refresh.
Variables weren't being interpolated during the Input phase, causing a
syntax error on the interpolation string. Adding `walkInput` to the
EvalTree operations prevents skipping the interpolation step.
