Setting ForcesProviderReplace on region mistakenly replaces resources in the same region

[t0yv0]

What happened?

Currently changing the region of AWS provider fails to move the resources to a new region and instead fails. While the
behavior is similarly unsatisfactory upstream, it would be nice if Pulumi could compute the correct plan (delete in
region A and create in region B).

Our first attempt to implement this tapped into a relevant feature here where DiffConfig call may indicate a replacement
of the provider, and this cascades to replace plans for all resources provisioned with that provider configuration,
which accomplishes the desired effect.

ForcesProviderReplace setting was introduced in the bridge, and DiffConfig reinstated, fixing
pulumi/pulumi-terraform-bridge#244 and #3497
demonstrated that this can make the AWS provider behave correctly on recent versions of Pulumi.

However, upgrade tests discovered a problem. While v3.111.1 of the CLI works, for resources provisioned on v3.86.0
version of the CLI (and possibly subsequent versions, we have not completed bisecting), Pulumi does not store region in
the state, causing the provider to erroneously conclude in DiffConfig that region is changing from empty to "us-west-2",
and replacing resources in the same region.

{
  "method": "/pulumirpc.ResourceProvider/DiffConfig",
  "request": {
    "urn": "urn:pulumi:test::test::pulumi:providers:aws::provider",
    "olds": {
      "version": "5.42.0"
    },
    "news": {
      "region": "us-west-2",
      "skipCredentialsValidation": "false",
      "skipMetadataApiCheck": "true",
      "skipRegionValidation": "true",
      "version": "5.42.0"
    },
    "oldInputs": {
      "version": "5.42.0"
    }
  },
  "response": {
    "replaces": [
      "region"
    ],
    "changes": "DIFF_SOME",
    "diffs": [
      "skipRegionValidation",
      "skipCredentialsValidation",
      "skipMetadataApiCheck"
    ],
    "detailedDiff": {
      "region": {
        "kind": "ADD_REPLACE",
        "inputDiff": true
      },
      "skipCredentialsValidation": {
        "inputDiff": true
      },
      "skipMetadataApiCheck": {
        "inputDiff": true
      },
      "skipRegionValidation": {
        "inputDiff": true
      }
    },
    "hasDetailedDiff": true
  }
}

Example

N/A

Output of pulumi about

N/A

Additional context

N/A

Contributing

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[t0yv0]

This got fixed in the bridge with pulumi/pulumi-terraform-bridge#1958