GH-5653 experimenting with query optimisation for union and optional implementated based on paper#5654

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GH-5653-query-optimisation-for-union-and-optional-implementated-based-on-papereclipse-rdf4j/rdf4j:GH-5653-query-optimisation-for-union-and-optional-implementated-based-on-paperCopy head branch name to clipboard