refactor(transformer): use `Option::get_or_insert_with` #19072

Job	Run time
Benchmark (lexer)	1m 34s
Build Linter Benchmark	3m 3s
Benchmark (parser)	1m 44s
Benchmark (transformer)	2m 58s
Benchmark (isolated_declarations)	2m 26s
Benchmark (semantic)	2m 3s
Benchmark (minifier)	2m 16s
Benchmark (codegen)	1m 38s
Benchmark (sourcemap)	2m 53s
Benchmark linter (0)	2m 54s
Benchmark linter (1)	1m 53s
Upload benchmarks	20s
	25m 42s

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