Fixed a serialization bug wrt PVT property flags when using subgraphs

[debaetsd]

This PR fixes incorrect SRP batcher incompatibility when sampling a PVT inside a subgraph.
This was due to a serialization bug wrt VT property flags

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[github-actions]

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[github-actions]

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[cdxntchou]

Woot!

[jessebarker]

LGTM