Add a fallback for detailed diff replaces where we fail to identify a key to be replaced

[VenelinMartinov]

We should consider adding a fallback for when the detailed diff algorithm fails to identify a property to be replaced but we know the resource must be replaced. We should also add a fallback for the reverse - we have identified a replace but one should not be present.

The engine trusts the detailed diff for these decisions.

Having the fallback which does a second pass over the detailed diff depending on the Update/Replace decision will make the detailed diff algorithm purely presentational.

The old detailed diff algorithm has a fallback for one side of this:

pulumi-terraform-bridge/pkg/tfbridge/provider.go

Line 1252 in 2a8b877

replaces = append(replaces, "__meta")

[VenelinMartinov]

We should also add a fallback for the reverse - we have identified a replace but one should not be present.