simplify extendSchemaImpl with mapSchemaConfig #776

Job	Run time
ci / Build 'npmDist' artifact	35s
ci / Build website	1m 4s
ci / Build 'denoDist' artifact	21s
ci / Check health of package-lock.json file	22s
ci / Run CodeQL security scan	1m 28s
ci / Run fuzzing tests	38s
ci / Check for commonly ignored files	4s
ci / Run integration tests	1m 23s
ci / Lint source files	1m 3s
ci / Run tests on Node v16	32s
ci / Run tests on Node v18	31s
ci / Run tests on Node v19	32s
Deploy to `deno` branch / deploy-artifact-as-branch	7s
Deploy to `npm` branch / deploy-artifact-as-branch	8s
	8m 48s

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