Backport of Don't write ephemeral outputs to state into v1.14

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Backport

This PR is auto-generated from #37821 to be assessed for backporting due to the inclusion of the label 1.14-backport.

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

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Don't backport until after 1.14 release.

Previously, the line state.SetOutputValue(n.Addr, val, n.Config.Sensitive) was (I think) mistakenly outside of a surrounding conditional. This isn't actually causing any problems at the moment, because ephemeral outputs are actually disallowed in root outputs anyway, and only root outputs are written to state but is still an inconsistency.

Also, Stacks and Test do allow root outputs to be ephemeral but for the moment don't record state files anywhere so also not an issue (yet).

This did discover an issue in Test though, as we do use the state file to check output values when requested which worked "by accident" before. Luckily, there is an easy fix for this which is to update the reference evaluator to use the named values object instead of the state file, and is safe to write ephemeral outputs into the named values since that is never made available externally. So, this PR also updates the GetOutput resolver to use the named values instead of the state file to resolve output references from test files.

Fixes #

Target Release

1.15.x

Rollback Plan

• If a change needs to be reverted, we will roll out an update to the code within 7 days.

Changes to Security Controls

Are there any changes to security controls (access controls, encryption, logging) in this pull request? If so, explain.

CHANGELOG entry

• This change is user-facing and I added a changelog entry.
• This change is not user-facing.

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Overview of commits

• 4fe1d68

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[liamcervante]

Closed in favour of #37850