refactor: clean up some code in `QueryExt::select_ids` #4675

Job	Run time
compilation-push	0s
compilation (windows-latest, query-engine-node-api) / compile query-engine-node-api @ windows-latest	10m 24s
compilation (ubuntu-latest, query-engine-node-api) / compile query-engine-node-api @ ubuntu-latest	5m 34s
compilation (windows-latest, query-engine) / compile query-engine @ windows-latest	12m 30s
compilation (windows-latest, schema-engine-cli) / compile schema-engine-cli @ windows-latest	10m 1s
compilation (windows-latest, prisma-fmt) / compile prisma-fmt @ windows-latest	4m 20s
compilation (ubuntu-latest, schema-engine-cli) / compile schema-engine-cli @ ubuntu-latest	5m 6s
compilation (ubuntu-latest, query-engine) / compile query-engine @ ubuntu-latest	5m 34s
compilation (ubuntu-latest, prisma-fmt) / compile prisma-fmt @ ubuntu-latest	1m 51s
	55m 20s

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