OverlappingFieldsCanBeMergedRule: Fix performance degradation #1609

Job	Run time
Diff content of NPM package	2m 24s
ci / Build website	3m 14s
ci / Check for commonly ignored files	4s
ci / Check health of package-lock.json file	48s
ci / Measure test coverage	59s
ci / Run fuzzing tests	58s
ci / Run integration tests	1m 49s
ci / Lint source files	1m 40s
ci / Run tests on Node v12	40s
ci / Run tests on Node v14	32s
ci / Run tests on Node v16	38s
ci / Run tests on Node v17	53s
ci / Build 'denoDist' artifact	48s
ci / Build 'npmDist' artifact	1m 29s
	16m 56s

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