Backport of Fix panics due to missing graph edges on empty modules or invalid refs into v1.8

[ghost]

Backport

This PR is auto-generated from #34985 to be assessed for backporting due to the inclusion of the label 1.8-backport.

The below text is copied from the body of the original PR.

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This PR fixes two crashes within Terraform v1.8.0. In both cases a module expansion was being missed, and then crashing when something tried to reference the missed module.

The first occurs when referencing an output that doesn't exist within the try() function. In this case the executing node was not getting connected to the module expansion node because the output node to connect doesn't exist. Now, the transform_reference transformer will unfold module call output references into simple module call references if the target node for a module call output does not exist.

The second occurs when referencing a module block directly (ie. not a module output), on a module that has no changes during the apply. The module expansion node was being removed as it had no direct references (as no changes from within the module). Now, the module expansion node implements the referenceable interface, and we'll connect nodes that reference the module directly both to the expansion node and the closer node. This will ensure the expansion of a module happens before anything that references it is processed.

Fixes #34976

Target Release

1.8.1

Draft CHANGELOG entry

BUG FIXES

• Fix crash in terraform plan when referencing a module output that does not exist within the try(...) function.
• Fix crash in terraform apply when referencing a module with no planned changes.

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Overview of commits

• 4e9ae3e

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