Use Box<str> for `Identifier

[MichaReiser]

• Use smol_str for Identifier
• Use boxed string for name

[codspeed-hq]

CodSpeed Performance Report

Merging #12100 will improve performances by 7.68%

_{Comparing name-box-str (e41728a) with main (47b2273)}

Summary

⚡ 4 improvements
✅ 26 untouched benchmarks

Benchmarks breakdown

	Benchmark	main	name-box-str	Change
⚡	parser[large/dataset.py]	5.4 ms	5 ms	+7.68%
⚡	parser[numpy/ctypeslib.py]	1,007.9 µs	958.4 µs	+5.16%
⚡	parser[pydantic/types.py]	2.2 ms	2.1 ms	+5.25%
⚡	parser[unicode/pypinyin.py]	329.3 µs	314 µs	+4.85%

[MichaReiser]

Closing in favor of #12101 which shows the most promising results