refactor(codegen): shorten `CodeBuffer::take_source_text` #19753

Job	Run time
Benchmark (lexer)	1m 41s
Benchmark (parser)	1m 38s
Build Linter Benchmark	3m 6s
Benchmark (transformer)	2m 12s
Benchmark (isolated_declarations)	1m 56s
Benchmark (semantic)	1m 43s
Benchmark (minifier)	2m 13s
Benchmark (codegen)	1m 39s
Benchmark (sourcemap)	1m 53s
Benchmark linter (0)	2m 57s
Benchmark linter (1)	2m 11s
Upload benchmarks	18s
	23m 27s

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