feat(traverse): introduce `MaybeBoundIdentifier` #22179

Job	Run time
Benchmark (lexer)	2m 33s
Benchmark (parser)	2m 8s
Benchmark (transformer)	2m 6s
Build Linter Benchmark	2m 56s
Benchmark (isolated_declarations)	2m 3s
Benchmark (semantic)	2m 1s
Benchmark (minifier)	2m 33s
Benchmark (codegen)	2m 27s
Benchmark (sourcemap)	1m 49s
Benchmark linter (0)	3m 5s
Benchmark linter (1)	1m 51s
Upload benchmarks	1m 4s
	26m 36s

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