Refactor has-oscal-namespace to use @nspredicate filter

[aj-stein-gsa]

Committer Notes

Closes #2113.

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[aj-stein-gsa]

@iMichaela this proposed change is changing extant syntax and removes the need of a custom function in the liboscal-java layer. It is low risk while improving developer experience and requiring less code with existing implementations. Have you had a chance to review it?