Assert no changes after a pulumi up --yes

[iwahbe]

Hello!

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Issue details

There are situations where we expect to see a diff during an upgrade, for example gcp v6 to v7 adds a new output field on many resources. When running replay tests for this scenario, it is ok that pulumi up shows +pulumiLabels. However, after running pulumi up --yes, we should be able to run pulumi preview --expect-no-changes and see no changes. For well behaved providers, it is always the case that pulumi up --yes && pulumi preview --expect-no-changes succeeds.

When an upgrade test asserts on a state transition (modeling pulumi up --yes, it should then assert that Diff(oldState, oldState) sends DIFF_NONE.

This will provide advanced warning for bugs such as https://pulumi.slack.com/archives/CBVJAP46L/p1698974120057579.

Affected area/feature

[t0yv0]

Implies #36 which was skipped for lack of time but looks like we really need that.