refactor(transformer/class-properties): `PrivatePropsStack` type #23292

Job	Run time
Benchmark (lexer)	1m 25s
Benchmark (parser)	1m 28s
Build Linter Benchmark	2m 38s
Benchmark (transformer)	1m 57s
Benchmark (isolated_declarations)	1m 54s
Benchmark (semantic)	1m 41s
Benchmark (minifier)	2m 10s
Benchmark (codegen)	1m 33s
Benchmark (sourcemap)	1m 50s
Benchmark linter (0)	3m 11s
Benchmark linter (1)	1m 48s
Upload benchmarks	14s
	21m 49s

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