Backport of actions: return an error if config is omitted but the schema has required attrs into v1.14

[github-actions]

Backport

This PR is auto-generated from #37626 to be assessed for backporting due to the inclusion of the label 1.14-backport.

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

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This PR fixes terraform's handling of nil action configurations. It will now properly return errors about missing required (not computed) attributes. This is done by substituting an hcl.EmptyBody in place of a nil config.

This would have gone a lot faster if I hadn't been slightly wrong about the hcl.EmptyBody from the start; I'd thought it was one of my error cases 😂😭

Fixes #

Target Release

1.14.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

• 2084154

• 8a889aa

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