PSS: Add tests showing `output` and `show` commands being used with PSS

[SarahFrench]

Following https://github.com/hashicorp/terraform/pull/37569, this PR demonstrates that the output and show commands work when pluggable state storage is in use.

The E2E tests rely on a test fixture resembling a fully initialised working directory, including some local state describing an instance of the terraform_data resource. That state is inspected by the commands in the tests.

The integration tests use an existing test fixture because some state_store config needs to be present for the test, but the state present in tests is contained within the mock provider definition.

Target Release

1.15.x

Rollback Plan

• [x] 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.
• [x] This change is not user-facing.