refactor(js_syntax): minor clean up

[Conaclos]

Summary

• Improve consistency of the documentation
• Use SyntaxResult instead of Option where possible.
• Remove unnecessary wrapping: use Option<X> instead of SyntaxResult<Option<X>>
• Use split_ascii_whitespace instead of split_whitespace for splitting HTML attribute values.
• Avoid some cloning and use TokenString instead of String for get_attribute_inner_string_text.

Test Plan

CI must pass.

[github-actions]

Parser conformance results on

js/262

Test result	main count	This PR count	Difference
Total	48591	48591	0
Passed	47399	47399	0
Failed	1192	1192	0
Panics	0	0	0
Coverage	97.55%	97.55%	0.00%

jsx/babel

Test result	main count	This PR count	Difference
Total	40	40	0
Passed	37	37	0
Failed	3	3	0
Panics	0	0	0
Coverage	92.50%	92.50%	0.00%

symbols/microsoft

Test result	main count	This PR count	Difference
Total	6586	6586	0
Passed	2208	2208	0
Failed	4378	4378	0
Panics	0	0	0
Coverage	33.53%	33.53%	0.00%

ts/babel

Test result	main count	This PR count	Difference
Total	680	680	0
Passed	608	608	0
Failed	72	72	0
Panics	0	0	0
Coverage	89.41%	89.41%	0.00%

ts/microsoft

Test result	main count	This PR count	Difference
Total	18615	18615	0
Passed	14270	14270	0
Failed	4345	4345	0
Panics	0	0	0
Coverage	76.66%	76.66%	0.00%

[codspeed-hq]

CodSpeed Performance Report

Merging #4513 will not alter performance

_{Comparing conaclos/jsx-minor-refactor (76689b6) with main (6c63919)}

Summary

✅ 99 untouched benchmarks