Backport of feat: add state_key for test run blocks into v1.11

[github-actions]

Backport

This PR is auto-generated from #36185 to be assessed for backporting due to the inclusion of the label 1.11-backport.

🚨

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The person who merged in the original PR is:
@liamcervante
This person should manually cherry-pick the original PR into a new backport PR,
and close this one when the manual backport PR is merged in.

merge conflict error: POST https://api.github.com/repos/hashicorp/terraform/merges: 409 Merge conflict []

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

---

While working on terraform module testing, i've been in need for a test case that ensure that a module upgrade is possible. Tests runs can only plan, apply and destroy a complete new infrastructure. My proposal allows to have multiple run blocks that targets the same infrastructure.

This could allow to make module upgrade tests, by ensuring the second apply using the new code still pass, or even checking that ressources does not get recreated.

Example code i want to implement :

run "old_code" {
  state_key = "module_test"

  variables {
    input1 = "toto"
  }

  module {
    source = "./test/old_code_path"
  }
}

run "new_code" {
  state_key = "module_test"

  variables {
    input1 = ""
  }

  module {
    source = "./test/new_code_path"
  }
}

Fixes #35080

PR Modifications ideas

I'm not sure about naming and where this option should be added

• Rename state_alias to state_key ?
• Move state_aliasfrom plan_options to run block ?

Target Release

1.11.x

Draft CHANGELOG entry

NEW FEATURES | UPGRADE NOTES | ENHANCEMENTS | BUG FIXES | EXPERIMENTS

• The terraform test command now supports a state_alias attribute in plan_option blocks during test runs. This feature allows multiple Terraform test runs to target the same infrastructure.

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Overview of commits

• 3a17ab1

• fd155ad

• 86e2ad8

• ccccf62

• 2e497b9

• 877b31c

[liamcervante]

The commits that failed here were the docs and changelog entries being added and then removed. We actually don't need these, so it's all good to merge.