This work was done against APIs that were already changed in the branch
before work began, and so it doesn't apply to the v0.12 development work.

To allow v0.12 to merge down to master, we'll revert this work out for now
and then re-introduce equivalent functionality in later commits that works
against the new APIs.

After a bunch of recent changes/rebasing our vendored dependencies got a
little out of sync w.r.t transitive dependencies through codebases that
are not themselves Go Modules yet.

Even if a provider doesn't indicate a specific attribute as the cause of
a resource operation error, we know the error relates to some aspect of
the resource, so we'll include that approximate information in the result
so that we don't produce user-hostile error messages with no context
whatsoever.

Later we can hopefully refine this to place the source range on the header
of the configuration block rather than on an empty part of the body, but
that'll require some more complex rework here and so for now we'll just
accept this as an interim state so that the user can at least figure out
which resource block the error is coming from.

This ensures more HCL1/HIL-like behaviors when dealing with nested blocks
that are not set in the configuration, which is important for
compatibility with helper/schema's validation logic.

This is a more specialized version of ConfigValueFromHCL2 which is
specifically for config values that represent the content of a block
body in the configuration.

By using the schema of that block we can more precisely emulate the old
HCL1/HIL behaviors by distinguishing attributes from blocks and applying
some slightly different behaviors for the handling of null values and
of empty collections that are representing the absense of blocks of a
particular type.

The last 2 broken tests will be hanlded later

Use the new SimpleDiff method of the provider so that the diff isn't
altered by ForceNew attributes.

Always set an "id" as RequiresReplace so core knows an instance will be
replaced, even if all ForceNew attributes are filtered out due to
ignore_changes.

The underlying bug that was causing this test to hang has since been
fixed.

If we don't override these then the tests can only pass on one platform.

This reinstates an old behavior that was lost in the reorganization of how
we deal with the -var and -var-file options.

This fix is verified by TestApply_planVars now passing.

In the new implementation of collecting variables I initially forgot the
JSON variant of terraform.tfvars.

This fix is verified by TestApply_varFileDefaultJSON now passing.

Terraform now handles any actual "diffing" of resource, and the existing
Diff functions are only used to shim the schema.Provider to the new
methods. Since terraform is handling what used to be the Diff, the
provider now should not modify the diff based on RequiresNew due to it
interfering with the ignore_changes handling.

The helper resource tests won't pass for now, as they use a
terraform.MockProvider which can't be used in the schema.Provider shims.

We need to ensure that a destroyed value is returned as such from apply

Tests often call Plan multiple times on the same context to verify there
are no changes, so we need to make sure changes don't accumulate.

We also need to convert legacy states for helper resource tests.

Since we need to know the index to know the result type for a tuple, we
need a special case here to deal with that situation and return
cty.DynamicVal; we can't predict the result type exactly until we know the
element type.

This was previously targeting the old state manager and state types, so it
needed some considerable rework to get it working again with the new state
types.

Since our new resource address syntax lacks the weird extra .deposed
special case we had before, we instead interpret addresses as
whole-instance addresses here and remove the deposed objects along with
the current one (if present), since this is more likely to match with
user expectations because we don't consider deposed objects to be
independently addressable in any other situation.

With that said, to be more explicit about what is going on we do now have
a -dry-run mode and maintain separate counts of current and deposed
instances so that we can expose that in the UI where relevant.

The tests in here are illustrating that this package is not yet finished,
but we plan to run a release before we finish this and so we'll skip those
tests for now with the intent of reinstating this again once we return
to finish this up.

We temporarily disabled this because it needed some further work to update
it for the new state models, which has now been done.

We no longer need the configuration objects for the outputs because the
state itself contains all of the information needed for displaying these.

We no longer support legacy remote state, so the behaviors these tests
were covering are no longer present.