Backport of import blocks are evaluated in the root module into v1.6

[teamterraform]

Backport

This PR is auto-generated from #33897 to be assessed for backporting due to the inclusion of the label 1.6-backport.

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

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Even though import block evaluation is done in conjunction with their target resource block, their evaluation scope must always be the containing module of the import block. Since import blocks currently are only valid in the root module, that means the context must always always be the root module.

The references for the import evaluation must also be scoped to the root module where the block was written. In order to accomplish that without adding a new import node type to the graph, we instead can opt to add a new method (and associated GraphNodeImportReferencer interface) which separates the import references from the config references. The ReferenceTransformer can then use the correct root module path to lookup the referenced subjects when they come from ImportReferences as opposed to References.

Fixes #33896

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