update use of deprecated ObjectNode.fields() method

[macfarla]

PR description

fields() is deprecated. properties() is almost the same but you don't get an iterator. propertyStream() gives you a stream so it made sense to use that instead

Fixed Issue(s)

Fixes some CodeQL deprecation warnings inc 1880

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[macfarla]

just double-checked, this is NOT covered by #8961 🙂