Ignore unexpanded paths when validating move statements.

[jbardin]

After each plan, the entire set of known move blocks must be validated. Sometimes the individual addresses may lie outside of paths which are expanded during the plan, either through the use of -target, or later changes to the configuration that make the moved obsolete.

Since instances.Set is only used after all instances have been processed, it should only handle known instances and not panic when given an address that traverses an unexpanded module. This will allow for validation of moved block which no longer apply to the current set of address to skip over addresses which cannot be expanded.

Fixes #30196
Fixes #30184

[apparentlymart]

I reviewed the source code of ValidateMoves to confirm that it only contains rules of the form "if given address exists in the set, error" and no rules of the form "if given address doesn't exist in the set, error", which is what I was hoping to confirm to give confidence that generating a partial set would be "safe" in the sense of potentially not catching things it would normally catch, rather than catching extra things it ought not to catch.

[lafentres]

this makes sense and i can confirm it fixes the error for the reproduction config i was able to create 👍🏼

[github-actions]

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