refactor(isolated_declarations): use aliases `ArenaBox` / `ArenaVec` #29414

Job	Run time
Benchmark (lexer)	2m 5s
Benchmark (parser)	1m 52s
Build Linter Benchmark	2m 45s
Benchmark (transformer)	2m 21s
Benchmark (isolated_declarations)	2m 3s
Benchmark (semantic)	2m 55s
Benchmark (minifier)	2m 17s
Benchmark (codegen)	4m 17s
Benchmark linter (0)	3m 32s
Benchmark linter (1)	2m 3s
Upload benchmarks	23s
	26m 33s

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