configs: More interpolation-only expr deprecations

[alisdair]

Extend the deprecation for interpolation-only expressions to include module calls, data sources, outputs, and locals.

This PR is targeting the 0.14.0 release. If merged, I'm not sure if it should be cherry-picked to 0.13.x or not. Thoughts?

Fixes #25430, fixes #25828, supersedes #25465.

[codecov]

Codecov Report

Merging #26105 into master will increase coverage by 0.00%.
The diff coverage is 100.00%.

Impacted Files	Coverage Δ
configs/module_call.go	69.23% <100.00%> (+1.66%)	⬆️
configs/named_values.go	67.96% <100.00%> (+0.76%)	⬆️
configs/resource.go	82.08% <100.00%> (+0.27%)	⬆️
terraform/node_resource_plan.go	91.80% <0.00%> (-1.64%)	⬇️

[apparentlymart]

This looks good to me! It'll be nice to expand the warning coverage to be more consistent.

Regarding when to release, I think it would make sense to release this in a 0.13.x, but I'd prefer to wait until a little later in the release period when we feel like we've taken care of the most significant upgrade-related blockers, so that folks upgrading won't feel pressured to deal with these deprecations at the same time as the upgrade steps. On our current trajectory that seems like maybe one more 0.13.x release to address some of the remaining upgrade concerns, and then we could issue one containing these deprecations. (Of course, we'll see how things really look once we've made the next 0.13.x release.)

[ghost]

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