feat(format/html): port JsxChildList formatting to HtmlElementList

[dyc3]

Summary

Given the similarity of JSX and HTML, I figured it would save a lot of time to simply port over the applicable portions of JSX formatting to HTML.

This PR attempts to do so for JsxChildList -> HtmlElementList.

Test Plan

quick_test should run without panicking.

[codspeed-hq]

CodSpeed Performance Report

Merging #3782 will degrade performances by 17.4%

_{Comparing 09-04-feat_format_html_port_jsxchildlist_formatting_to_htmlelementlist_ (dacc167) with main (eff4295)}

Summary

❌ 1 regressions
✅ 106 untouched benchmarks

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

	Benchmark	main	09-04-feat_format_html_port_jsxchildlist_formatting_to_htmlelementlist_	Change
❌	eucjp_1600564308684076393.json[uncached]	953.4 µs	1,154.2 µs	-17.4%

[github-actions]

Parser conformance results on

js/262

Test result	main count	This PR count	Difference
Total	48511	48511	0
Passed	47320	47320	0
Failed	1191	1191	0
Panics	0	0	0
Coverage	97.54%	97.54%	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	6569	6569	0
Passed	2202	2202	0
Failed	4367	4367	0
Panics	0	0	0
Coverage	33.52%	33.52%	0.00%

ts/babel

Test result	main count	This PR count	Difference
Total	671	671	0
Passed	599	599	0
Failed	72	72	0
Panics	0	0	0
Coverage	89.27%	89.27%	0.00%

ts/microsoft

Test result	main count	This PR count	Difference
Total	18418	18418	0
Passed	14100	14100	0
Failed	4318	4318	0
Panics	0	0	0
Coverage	76.56%	76.56%	0.00%

[chansuke]

Is it useful to add a comment explaining the newline detection?

Suggested change

	} else if c == '\n' {
	has_newline = true;
	}
	} else if c == '\n' {
	// A newline is detected. This is tracked separately,
	// potentially to differentiate text with just line breaks from other whitespace.
	has_newline = true;
	}

[dyc3]

This is explained in the doc comment for the function.

[chansuke]

Is this space intentional?

[dyc3]

This is mostly copied straight from the formatter for JsxChildList.

[dyc3]

I think I've resolved the comments thing in other PRs. I've tested this with the prettier test suite, and it gets most of the way there in terms of compatibility.